Variability in Sentinel Lymph Node Locations in Endometrial Cancer: A Single-Center Study and Literature Review

Variability in Sentinel Lymph Node Locations in Endometrial Cancer: A Single-Center Study and Literature Review | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Variability in Sentinel Lymph Node Locations in Endometrial Cancer: A Single-Center Study and Literature Review Wiktor Szatkowski, Karolina Pniewska, Małgorzata Nowak-Jastrząb, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7419838/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Sentinel lymph node biopsy (SLNB) has become a widely accepted alternative to systematic lymphadenectomy in endometrial cancer (EC), reducing surgical morbidity without compromising diagnostic accuracy. However, the anatomical variability of sentinel lymph node (SLN) locations remains insufficiently understood, with substantial differences reported across studies. This study analyzed SLN distribution in a large single-center cohort and compared the findings with published data. Methods We retrospectively analyzed 292 patients with EC treated at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch (2016–2025). All underwent SLN mapping using technetium-99m (Tc99m), indocyanine green (ICG), Patent Blue, or their combinations. Bilateral detection failures were managed according to an established intraoperative algorithm. SLNs were classified anatomically, and outcomes were compared across mapping techniques. Histopathological assessment included ultrastaging. Results A total of 526 SLNs were identified (mean 1.8 per patient). The most common locations were the obturator (48.7%) and internal iliac (25.1%) regions. Bilateral detection was achieved in 87.0% of patients, unilateral in 12.0%, and no detection in 1.0%. Metastases were found in 41 SLNs (7.8%) from 34 patients (11.6%), most frequently in obturator (41.5%) and internal iliac (17.1%) nodes. The use of tracer combinations (ICG + Tc99m or Tc99m + Patent Blue) improved detection when preoperative Tc99m mapping was incomplete. Para-aortic SLNs were rare (1.5%) but carried a significantly higher risk of metastasis. Conclusions SLNB is an effective and safe method for nodal assessment in EC, with the obturator and internal iliac regions being the most frequent SLN sites. Variability in SLN locations appears to depend on mapping technique, tracer type, and surgical access. Standardization of procedures and prospective comparative studies are essential to further optimize SLNB in gynecologic oncology. endometrial cancer sentinel lymph node mapping technetium-99m indocyanine green lymphatic anatomy tracer combinations metastases Figures Figure 1 1. Introduction Endometrial cancer is the most common gynecological malignancy in developed countries [ 1 ]. Sentinel lymph node biopsy (SLNB) is now widely accepted as an alternative to systematic pelvic lymphadenectomy, reducing surgical morbidity while maintaining high diagnostic accuracy [ 2 – 4 ]. The key element of this procedure is the identification of sentinel lymph nodes (SLNs), which are the first nodes to receive lymphatic drainage from the primary tumor. The incidence of lymph node metastases is approximately 20% in high-risk patients and 3–9% in low-risk patients [ 5 , 6 ]. Previous studies have demonstrated considerable variability in the anatomical location of SLNs in endometrial cancer [ 7 – 11 ]. This heterogeneity may result from multiple factors, including disease stage, tracer injection site and technique, tracer type, patient characteristics (e.g., BMI, histologic subtype), and surgeon experience [ 12 ]. Importantly, SLNB has been shown to be oncologically safe even in high-risk subgroups, such as patients with serous histology [ 13 ], deep myometrial invasion [ 14 ], or carcinosarcoma [ 15 ]. Compared with systematic lymphadenectomy, SLNB does not compromise recurrence-free or overall survival, while significantly reducing the risk of lymphedema and improving physical function and quality of life [ 16 , 17 ]. Meta-analyses confirm that SLNB is an effective and less invasive alternative to complete lymphadenectomy, particularly when complemented by side-specific lymphadenectomy in cases of mapping failure [ 17 – 20 ]. This approach reduces the risk of both undertreatment and overtreatment, which remain important challenges in clinical practice [ 21 ]. Large prospective trials, including SENTI-ENDO [ 22 ], FIRES [ 9 ], and SHREC [ 18 ], have validated the diagnostic performance of SLNB, demonstrating high detection rates and low false-negative rates. Currently, cervical tracer injection is preferred, as it ensures higher bilateral detection and lower rates of technical failure [ 24 , 25 ]. According to NCCN guidelines, the effectiveness and safety of SLNB depend on adherence to a structured algorithm, which includes side-specific lymphadenectomy in the event of failed mapping and the removal of all suspicious lymph nodes regardless of SLN visualization [ 2 ]. Similarly, the ESGO–ESTRO–ESP [ 3 ], ESMO [ 4 ], and NCCN [ 2 ] guidelines recognize SLNB as a reliable method for lymph node assessment in patients with low-, intermediate-, and selected high-risk endometrial cancer. A better understanding of SLN location variability is essential to optimize mapping efficacy and ensure accurate disease staging. The aim of this study was to analyze SLN locations in a single-center cohort of patients with endometrial cancer and to compare the findings with published literature. This comparison enables evaluation of the anatomical diversity of SLNs and exploration of potential reasons for discrepancies, including anatomical, technical, and clinical factors influencing mapping success. 2. Materials and Methods 2.1. Study Design and Setting This retrospective cohort study was conducted at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland, between December 2016 and April 2025. Patients with endometrial cancer (EC) preoperatively classified as FIGO stage I–II (2009 classification) based on clinical and imaging assessments [ 26 ] and who underwent SLN mapping were included. The study protocol was approved by the Ethics Committee of the National Research Institute of Oncology (approval no. 10/2025). All data were anonymized, and informed consent was obtained from patients in accordance with ethical guidelines. 2.2. Inclusion and Exclusion Criteria Eligible patients had histologically confirmed endometrial cancer (FIGO stages IA–IVB), received no neoadjuvant therapy, and had complete clinical and pathological data. Exclusion criteria included age below 18 or above 85 years and contraindications to surgical treatment. Of 306 patients initially screened for SLN mapping, 14 were excluded due to incomplete clinical data or advanced non-endometrial malignancies, resulting in a final cohort of 292 patients. 2.3. Sentinel Lymph Node Identification Procedure Surgical staging included total hysterectomy, bilateral salpingo-oophorectomy, and SLN mapping, performed via laparoscopy (n = 242) or laparotomy (n = 50) based on clinical indications (e.g., tumor size, BMI, comorbidities). SLN detection utilized technetium-99m (Tc99m), indocyanine green (ICG), Patent-Blue, or their combinations (primarily Tc99m with ICG), adapted from Szatkowski et al. [ 27 ]. 2.3.1. Radioactive Tracer Administration (Tc99m) Technetium-99m-labeled human albumin colloid (NanoColl, GE Healthcare, Chicago, IL, USA) was injected into the cervical stroma at the 3 and 9 o’clock positions, equally divided between superficial (2–3 mm) and deep (10–15 mm) layers using 21G needles. Two protocols were used: a short protocol (40 MBq, same-day surgery) for logistical feasibility and a long protocol (120 MBq, day before surgery) for enhanced tracer uptake. The Mediso AnyScan gamma camera (Mediso, Budapest, Hungary) facilitated preoperative and intraoperative SLN localization. 2.3.2. Dye Administration Two dyes were administered, either alone or in combination with Tc99m: (1) indocyanine green (ICG), 0.5 mL (1.25 mg) diluted in 5 mL sterile water, injected at the same cervical positions; (2) Patent Blue, 2 mL in total (1 mL per site). Dyes were injected 15–30 min before surgery. Tc99m was used in all cases as the primary tracer. If preoperative scintigraphy showed incomplete or unilateral SLN detection, ICG or Patent Blue was added intraoperatively. ICG was applied whenever fluorescence imaging equipment was available. 2.3.3. Sentinel Lymph Node Identification SLNs were detected intraoperatively using a gamma probe (Gamma Finder 2, World of Medicine, Berlin, Germany) for Tc99m and a laparoscopic fluorescence imaging system (Visionsense 3DHD and IR Fluorescence V, Medtronic, Dublin, Ireland) for ICG and Patent Blue. SLNs were classified into obturator, external iliac, internal iliac, common iliac, para-aortic, parametrial, and presacral regions. All excised SLNs were verified ex vivo with the gamma probe. In laparotomy cases, tracer-based detection was supplemented by visual and manual inspection. 2.4. Histopathological Examination Excised sentinel lymph nodes (SLNs) were fixed in 10% formalin, sliced at 2 mm intervals, and stained with hematoxylin and eosin (H&E). Ultrastaging was performed using serial sectioning and immunohistochemistry for cytokeratins to detect isolated tumor cells (ITC), micrometastases (MM), and macrometastases (MAC). 2.5. Statistical Analysis Data were analyzed using IBM SPSS Statistics v25.0. Qualitative variables, including SLN detection rates and anatomical locations, were summarized as frequencies (n) and percentages (%). Detection rates across tracer techniques were compared using the chi-squared test or Fisher’s exact test, with a two-tailed p-value < 0.05 considered statistically significant. Odds ratios (OR) with 95% confidence intervals (CI) were calculated to assess the likelihood of metastatic involvement in specific SLN locations. Quantitative variables (e.g., age, number of SLNs) were analyzed using t-tests or Mann-Whitney U tests as appropriate. 2.6. SLN Evaluation Parameters The following metrics were evaluated: Bilateral detection rate (BDR): Percentage of patients with SLNs identified on both pelvic sides. Unilateral detection rate: Percentage of patients with SLNs identified on one pelvic side. Para-aortic only detection: Percentage of patients with SLNs identified solely in the para-aortic region. Non-detection rate: Percentage of patients with no SLNs identified. Number of SLNs per patient: Average number of SLNs detected per procedure. Metastatic involvement rate: Percentage of patients with metastatic SLNs. 3. Results 3.1. Patient Characteristics A total of 292 patients were included, with a median age of 68,2 years (range: 37–84) and a median BMI of 31,1 kg/m² (range: 19–53) (Table 1 .). The majority had endometrioid histology (80,8%), most commonly Grade 1 (39,7%) or Grade 2 (32,9%). Serous and clear-cell carcinomas accounted for 8,2% and 5,5% of cases, respectively, and 12 patients (4,1%) had complex atypical hyperplasia. According to the 2009 FIGO staging system, stage IA (35,9%) and IB (30,8%) were predominant, with advanced stages (II: 14,7%, IIIA–C2: 14,0%, IVB: 0,3%) identified post-surgically. Surgical treatment was performed via laparoscopy (82,9%) or laparotomy (17,1%). 3.2. SLN Mapping Protocols and Detection Rates Mapping protocols are summarized in Table 2 . Tc99m alone was the most frequent approach (38,3%), followed by ICG alone (37,0%) in selected cases due to logistical constraints, Tc99m + Patent Blue (16,4%), and Tc99m + ICG (8,2%). Tc99m was the initial tracer in most cases, with additional tracers applied intraoperatively for incomplete preoperative scintigraphy mapping. The overall bilateral detection rate was 87,0% (254/292 patients), unilateral detection occurred in 12,0% (35/292), and no SLN was identified in 1,0% (3/292). The mean number of SLNs per patient was 1,8 (median: 1,9; range: 0–4). 3.3. Anatomical Distribution and Metastatic Involvement A total of 526 SLNs were identified across 292 patients (Table 3, Fig. 1 ). The most frequent anatomical locations were the obturator region (48,7%), internal iliac region (25,1%), external iliac (16,0%), and common iliac (7,2%) regions. Para-aortic (1,5%), presacral (1,1%), and parametrial (0,4%) nodes were rare. Metastases were detected in 41 SLNs (7,8% of all SLNs) from 34 patients (11,6% of the cohort), including 27 with unilateral metastases (1 SLN each) and 7 with bilateral metastases (2 SLNs each). The most frequent metastatic sites were the obturator region (17 SLNs, 41,5%), internal iliac nodes (7 SLNs, 17,1%), and external iliac nodes (6 SLNs, 14,6%), consistent with SHREC [ 23 ] and FIRES [ 9 ] reporting 95–98% of SLN metastases in pelvic regions. Para-aortic SLNs (8 SLNs, 1,5%) showed a significantly higher likelihood of metastatic involvement (OR = 13,00, 95% CI: 3,13–54,02, p = 0,0018). Most metastases were macrometastases (MAC, 32/41, 78,0%), with a predominance in the obturator region (15/17, 88,2%) and external iliac nodes (5/6, 83,3%). MAC were 3,09 times more likely in the obturator region compared to low-volume metastatic disease (LVMD; isolated tumor cells + micrometastases) when contrasted with other locations (OR = 3,09, 95% CI: 0,55–17,24, p = 0,66, not statistically significant). The distribution of metastasis types is presented in Table 3. Figure 1 shows the proportional distribution of SLNs and metastatic SLNs by anatomical location, with percentages in the “SLNs detected” category referring to all SLNs (n = 526) and in the “Metastatic SLNs” category referring to metastatic SLNs (n = 41) in 34 patients. Table 1 Clinical-Pathological Features and Mapping Outcomes Characteristics n (%) or median (range) Patients, n (%) 292 (100) Age (years) median: 68.2 (range: 37–84) BMI (kg/m²) median: 31.1 (range: 19–53) Histology, n (%) – Complex atypical hyperplasia 12 (4.1) – Endometrioid Grade 1 116 (39.7) – Endometrioid Grade 2 96 (32.9) – Endometrioid Grade 3 24 (8.2) – Serous 24 (8.2) – Clear-cell 16 (5.5) – Other 4 (1.4) Stage (2009 FIGO), n (%) – IA 105 (35.9) – IB 90 (30.8) – II 43 (14.7) – IIIA 7 (2.4) – IIIC1 31 (10.6) – IIIC2 3 (1.0) – IVB 1 (0.3) Number of SLNs mean 1.8 (median: 1.9, range: 0–4) Surgical approach, n (%) – Laparoscopy 242 (82.9) – Laparotomy 50 (17.1) Notes: Percentages may not sum to 100,0% due to rounding. Data collected from the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland (2016–2025). Advanced stages (II–IVB) were identified post-surgically. Table 2 Mapping protocols and their application in the study cohort Mapping protocol n patients (%) Application strategy in this study Tc99m alone 112 (38.3) Standard initial protocol; performed in all cases as the first step with preoperative planar scintigraphy. Proceeded directly to surgery if bilateral SLN visualization was achieved. Tc99m + ICG 24 (8.2) Added intraoperatively when preoperative Tc99m mapping was incomplete (unilateral or no SLN visualized) or when intraoperative conditions favored fluorescence imaging; choice also influenced by equipment availability. Tc99m + Patent Blue 48 (16.4) Alternative complementary method used in cases of incomplete Tc99m mapping, selected based on surgeon’s discretion, patient factors, or technical considerations. ICG alone 108 (37.0) Used in selected cases when Tc99m was not administered, mainly due to logistical or technical reasons, while ensuring full adherence to the mapping algorithm. Percentages may not sum to 100% due to rounding. Detection outcomes: Bilateral detection: 254/292 (87.0%) Unilateral detection: 35/292 (12.0%) No SLN detected: 3/292 (1.0%) Notes: Tc99m = technetium-99m; ICG = indocyanine green. Consistent with widespread international use, ICG was broadly applied in our cohort whenever fluorescence imaging was available, whereas Tc99m remained the initial tracer in all cases. Additional tracers were applied intraoperatively according to predefined criteria when preoperative scintigraphy showed incomplete bilateral SLN detection. Table 3. Sentinel Lymph Node Characteristics in Endometrial Cancer Location SLNs detected, n (% of all SLNs) SLNs with metastases, n (% of all with metastases) ITC, n (%) MM, n (%) MAC, n (%) Internal iliac 132 (25.1) 6 (14.6) 1 (16.7) 0 (0.0) 5 (83.3) Obturator 256 (48.7) 17 (41.5) 0 (0.0) 2 (11.8) 15 (88.2) Common iliac 38 (7.2) 5 (12.2) 0 (0.0) 2 (40.0) 3 (60.0) External iliac 84 (16.0) 7 (17.1) 1 (14.3) 1 (14.3) 5 (71.4) Para-aortic 8 (1.5) 4 (9.8) 2 (50.0) 0 (0.0) 2 (50.0) Parametrial 2 (0.4) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) Presacral 6 (1.1) 2 (4.9) 0 (0.0) 0 (0.0) 2 (100.0) Total 526 (100.0) 41 (100.0) 4 (9.8) 5 (12.2) 32 (78.0) Abbreviations: SLN, sentinel lymph node; ITC, isolated tumor cells; MM, micrometastases; MAC, macrometastases. Notes : Data from 292 patients with endometrial cancer (FIGO IA–IVB confirmed histologically, preoperative FIGO I–II) or complex atypical hyperplasia (4,1%, 12 patients), treated at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland (2016–2025). A total of 526 SLNs were detected using Tc99m, indocyanine green (ICG), Patent Blue, or their combinations. Mean number of SLNs per patient: 1,8 (median: 1,9, range: 0–4). Percentages in the “SLNs detected” column refer to the total number of SLNs (526). Percentages in the “SLNs with metastases” column refer to 41 SLNs with metastases in 34 patients (27 with unilateral metastases, 1 SLN each; 7 with bilateral metastases, 2 SLNs each). Percentages in the ITC, MM, and MAC columns refer to metastatic SLNs in each location. Percentages may not sum to 100,0% due to rounding. 4. Discussion 4.1. Anatomical variability of SLN localization In our study, 526 sentinel lymph nodes (SLNs) were identified in 292 patients with endometrial cancer or atypical endometrial hyperplasia (Table 3, Fig. 1). The most frequent sites were the obturator fossa (48.7%), internal iliac (25.1%), external iliac (16.0%), and common iliac (7.2%) regions. Less frequent locations included para-aortic (1.5%), presacral (1.1%), and parametrial (0.4%) nodes. Metastases were detected in 41 SLNs in 34 patients (11.6% of the cohort), including seven bilateral cases. They were most commonly located in the obturator fossa (41.5%), along the internal iliac (17.1%) and external iliac arteries (14.6%), consistent with previous observations that 95–98% of SLN metastases are located within the pelvis [10]. Although para-aortic nodes accounted for only 1.5% of all SLNs, the risk of metastasis was significantly higher in this region (OR = 13.00; 95% CI: 3.13–54.02; p = 0.0018). Most metastases were macrometastases (78.0%), particularly in the obturator region (88.2%). The relatively low prevalence of low-volume disease (LVMD: ITC + MM; 22.0%) compared with reports of up to 50% [28] may reflect differences in ultrastaging protocols or cohort characteristics. While the prognostic significance of macro- and micrometastases is well established, the clinical role of ITCs remains unclear [29,30]. Ongoing prospective studies (ALICE, SNEC [31]) may help to define their impact. 4.2. Impact of injection technique and surgical approach on SLN localization The site of injection and surgical technique have a significant influence on SLN localization [32,33]. In our cohort, which included both laparoscopic and open procedures, SLNs were most frequently identified in the obturator fossa (48.7%) and along the internal iliac artery (25.1%). These findings are in line with FIRES [9], How et al. [7], and Lührs et al. [10]. Huber et al. [11], using the transvaginal vNOTES approach, reported a markedly higher proportion of obturator nodes (81.5%), most likely attributable to the surgical technique itself. Anatomical variability is also influenced by individual lymphatic drainage pathways. Kimmig et al. [34] and Persson et al. [23] described three main lymphatic routes from the uterus: external iliac, obturator, and para-aortic. In our study, cervical injections were used, which preferentially highlight pelvic and obturator drainage pathways compared with fundal injections [35]. The choice of tracers (Tc99m, ICG, Patent Blue [7]) also affected the distribution of SLNs. Rare sites, such as para-aortic or presacral nodes, were observed at frequencies similar to previous reports [7,10,32]. 4.3. Detection rates and tracer performance The overall SLN detection rate was 98.9%, with bilateral detection in 87.0%. These figures are slightly lower than in SHREC (100% and 91.9% [23]), likely due to population differences and less frequent use of reinjection protocols in our cohort. Detection rates improved in later years with increased use of tracer combinations (ICG + Tc99m in 8.2% and ICG + Patent Blue in 16.4%) and reinjection of ICG, consistent with SHREC recommendations [23]. ICG demonstrates higher sensitivity than blue dyes [8,24,25]. In the study by Ehrisman et al. [36], the detection rate of metastatic SLNs was 90% with ICG versus 75% with Patent Blue (p = 0.05). Limitations of blue dyes include rapid washout, reduced penetration in obese patients, and diffusion into parametrial tissues [37-39]. Despite its diagnostic superiority, ICG carries the risk of misidentifying secondary nodes, leading to removal of superficial non-sentinel nodes instead of true SLNs [40]. Additional pitfalls such as “empty nodal packets” (5–6% of cases) [40] and the “glow effect” during delayed assessment [33,40-41] increase the risk of false mapping. For this reason, mapping is recommended at the beginning of the procedure in a clean surgical field. In our study, the obturator fossa was the dominant site of metastatic SLNs (41.5%, 17/41), confirming the observations of Lührs et al. (48.6% [10]). Clinically, this highlights the need for meticulous exploration of the obturator region, despite technical challenges. In obese patients, ICG fluorescence may be limited, while in older patients tortuous vessels along the external iliac artery hinder access. In such cases, Tc99m, alone or combined with ICG, enabled more effective SLN detection. The advantage of Tc99m lies in its physicochemical properties: larger particle size (human albumin colloid 50–200 nm [19]) ensures longer nodal retention and minimizes diffusion to secondary nodes [42,43], effectively preventing removal of second-tier nodes seen with ICG. In our previous study using Tc99m alone, the mean number of nodes per SLN region was 1.4 [44], compared with 1.8 in the present cohort with multiple tracer combinations. Fewer nodes suggest higher selectivity of Tc99m, while the combination of ICG + Tc99m improved mapping efficacy in anatomically challenging cases (obesity, deep obturator nodes). 4.4. Standardization and surgical algorithms Differences in SLN detection efficacy across studies may reflect variations in injection protocols, tracer types and doses, and surgical techniques. According to NCCN and ESGO-ESTRO-ESP guidelines [2,3], the SLN algorithm should include unilateral lymphadenectomy in cases of failed mapping and mandatory removal of suspicious nodes. These procedures were followed in our study, minimizing the risk of false-negative results, though para-aortic metastases may still be missed. Our findings demonstrated high sensitivity and negative predictive value of SLN biopsy, consistent with FIRES [9] and SENTI-ENDO [22]. The lower bilateral detection rate (87.0%) compared with SHREC (91.9% [23]) may partly reflect a learning-curve effect, as emphasized by Khoury-Collado et al. [45] and Tucker [46], who reported improved detection after >30–40 procedures. A similar trend of increasing detection efficacy was observed in our cohort over time. The two-step mapping strategy described by Kim et al. [35] could improve the detection of rare para-aortic SLNs (1.5% in our study), which in some cases represent the only site of metastasis (0.5–3.8% [47]). The lack of standardization in tracer type, injection technique, and ultrastaging protocols hampers comparability across studies and may contribute to discrepancies in the reported detection of rare or micrometastatic disease [39]. 4.5. Study limitations Our study has several limitations. First, it was conducted in a single institution, limiting the generalizability of results. Second, different surgical approaches (laparotomy, laparoscopy) and tracer combinations were used during the study period, which may have influenced outcomes. Third, reinjection of ICG and standardized two-step mapping protocols were not routinely performed, potentially underestimating rare SLN locations. Finally, we did not analyze in detail the effect of the surgical learning curve or clinical factors such as obesity or prior treatments. 4.6. Future perspectives Future studies should focus on multicenter analyses with harmonized SLN protocols, including standardized tracer doses and types, injection techniques, and uniform ultrastaging assessment. Particular attention should be given to rare SLN localizations (paraaortic, presacral), which, although infrequent, may carry clinical significance. Another important direction is evaluating the clinical impact of low-volume metastases (ITC, MM) on treatment decisions. Comparative analyses of tracer combinations in high-risk groups (obesity, non-endometrioid histology) and integration of preoperative imaging (SPECT/CT, two-step protocols) and digital tools (AI) may further enhance the accuracy and reproducibility of SLN detection. 5. Conclusion Sentinel lymph node biopsy is an effective and safe method for lymph node assessment in endometrial cancer, allowing a reduction in the extent of lymphadenectomy while maintaining high diagnostic sensitivity. In our cohort, the obturator region was the most frequent site of both overall and metastatic SLNs, emphasizing the need for careful exploration of this area despite technical challenges. The use of combined tracers (Tc99m + ICG/Patent Blue) increased mapping precision, reduced the risk of “empty” nodal packets, and improved metastasis detection. Further standardization of injection protocols, dose optimization, and the incorporation of preoperative imaging may enhance detection rates, particularly in rare localizations such as para-aortic nodes. Abbreviations SLNB : Sentinel lymph node biopsy EC: endometrial cancer SLN: sentinel lymph node Tc99m: technetium-99m ICG : indocyanine green NCCN: National Comprehensive Cancer Network ESGO-ESTRO-ESP: European Society of Gynaecological Oncology - European Society for Radiotherapy and Oncology - European Society of Pathology ESMO: European Society for Medical Oncology BMI: body mass index H&E : hematoxylin and eosin ITC : detect isolated tumor cells MM: micrometastases MAC: macrometastases BDR: Bilateral detection rate LVMD: low-volume metastatic disease Declarations Funding This research received no external funding. Conflicts of Interest The authors declare that they have no conflicts of interest. Ethics Approval This study was approved by the Ethics Committee of the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland (Approval No. 10/2025), and was conducted in accordance with the Declaration of Helsinki. Consent to Participate Written informed consent was obtained from all participants. Consent for Publication Not applicable. Availability of Data and Materials Statistical results reported in this article are publicly available. Access to raw patient-level data is restricted and may be obtained from the corresponding author upon reasonable request, subject to approval by the Ethics Committee of the Maria Sklodowska-Curie National Research Institute of Oncology. Authors’ Contributions Study conception and design: WS,PB,TB. Material preparation and data collection: WS,KP,KK,MNJ. Histopathological evaluation: JR. Statistical analysis: WS, KP. First draft of the manuscript: WS. Critical review and editing: KP, KK, MNJ,JR,TB and PB. All authors read and approved the final manuscript. Acknowledgements: None. References Sung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, Bray F. 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Lymph node dissection in endometrial cancer and clinical outcome: A population-based study in 5546 patients. Gynecol Oncol. 2019;154(1):65–71. doi: 10.1016/j.ygyno.2019.04.002 . Ballester M, Dubernard G, Lécuru F, Heitz D, Mathevet P, Marret H, Querleu D, Golfier F, Leblanc E, Rouzier R, Daraï E. Detection rate and diagnostic accuracy of sentinel-node biopsy in early stage endometrial cancer: a prospective multicentre study (SENTI-ENDO). Lancet Oncol. 2011;12(5):469–76. doi: 10.1016/S1470-2045(11)70070-5 . Persson J, Salehi S, Bollino M, Lönnerfors C, Falconer H, Geppert B. Pelvic Sentinel lymph node detection in High-Risk Endometrial Cancer (SHREC-trial)-the final step towards a paradigm shift in surgical staging. Eur J Cancer. 2019;116:77–85. doi: 10.1016/j.ejca.2019.04.025 . Kang S, Yoo HJ, Hwang JH, Lim MC, Seo SS, Park SY. Sentinel lymph node biopsy in endometrial cancer: meta-analysis of 26 studies. Gynecol Oncol. 2011;123(3):522–7. doi: 10.1016/j.ygyno.2011.08.034 . Khoury-Collado F, Abu-Rustum NR. Lymphatic mapping in endometrial cancer: a literature review of current techniques and results. Int J Gynecol Cancer. 2008 Nov-Dec;18(6):1163–8. doi: 10.1111/j.1525-1438.2007.01188.x . Female Genital Tumours. WHO Classification of Tumours, 5th ed.; World Health Organization: Geneva, Switzerland, 2020; Volume 4. Szatkowski W, Pniewska K, Janeczek M, Ryś J, Banaś T, Muzykiewicz K, Iwańska E, Jakubowicz J, Karolewski K, Szadurska A, Blecharz P. The Assessment of Sentinel Lymph Node Mapping Methods in Endometrial Cancer. J Clin Med. 2025;14(3):676. doi: 10.3390/jcm14030676 . Zhai L, Zhang X, Cui M, Wang J. Sentinel Lymph Node Mapping in Endometrial Cancer: A Comprehensive Review. Front Oncol. 2021;11:701758. doi: 10.3389/fonc.2021.701758 . Todo Y, Kato H, Okamoto K, Minobe S, Yamashiro K, Sakuragi N. Isolated tumor cells and micrometastases in regional lymph nodes in stage I to II endometrial cancer. J Gynecol Oncol. 2016;27(1):e1. doi: 10.3802/jgo.2016.27.e1 . Münzová D, Bretová P, Hausnerova J, Bednaříková M, Minář L, Weinberger V. Low-volume regional lymph node metastasis in endometrial cancer – 2024 update. Ceska Gynekol. 2025;90(2):158–162. English. doi: 10.48095/cccg2025158 . Kim YN, Kim YT. Sentinel lymph node biopsy in high-risk endometrial cancer: performance, outcomes, and future avenues. Obstet Gynecol Sci. 2022;65(5):395–405. doi: 10.5468/ogs.22146 . Restaino S, Buda A, Puppo A, Capozzi VA, Sozzi G, Casarin J, Gallitelli V, Murgia F, Vizzielli G, Baroni A, Corrado G, Pasciuto T, Ferrari D, Novelli A, Berretta R, Legge F, Vizza E, Chiantera V, Ghezzi F, Landoni F, Scambia G, Fanfani F. Anatomical distribution of sentinel lymph nodes in patients with endometrial cancer: a multicenter study. Int J Gynecol Cancer. 2022;32(4):517–524. doi: 10.1136/ijgc-2021-003253 . Szatkowski W, Słonina D, Ryś J, Blecharz P, Banaś T, Nowak-Jastrząb M. The role of technetium-99m isotope in sentinel lymph node identification in gynecological cancers. Rep Pract Oncol Radiother. 2025;30(2):257–268. doi: 10.5603/rpor.105251 . Kimmig R, Thangarajah F, Buderath P. Sentinel Lymph node detection in endometrial cancer - Anatomical and scientific facts. Best Pract Res Clin Obstet Gynaecol. 2024;94:102483. doi: 10.1016/j.bpobgyn.2024.102483 . Kim YN, Eoh KJ, Lee JY, Nam EJ, Kim S, Kim YT, Kim SW. Comparison of outcomes between the one-step and two-step sentinel lymph node mapping techniques in endometrial cancer. Int J Gynecol Cancer. 2020;30(3):318–324. doi: 10.1136/ijgc-2019-000962 . Ehrisman J, Secord AA, Berchuck A, Lee PS, Di Santo N, Lopez-Acevedo M, Broadwater G, Valea FA, Havrilesky LJ. Performance of sentinel lymph node biopsy in high-risk endometrial cancer. Gynecol Oncol Rep. 2016;17:69–71. doi: 10.1016/j.gore.2016.04.002 . Sinno AK, Fader AN, Roche KL, Giuntoli RL 2nd, Tanner EJ. A comparison of colorimetric versus fluorometric sentinel lymph node mapping during robotic surgery for endometrial cancer. Gynecol Oncol. 2014;134(2):281–6. doi: 10.1016/j.ygyno.2014.05.022 . Du J, Li Y, Wang Q, Batchu N, Zou J, Sun C, Lv S, Song Q, Li Q. Sentinel lymph node mapping in gynecological oncology. Oncol Lett. 2017;14(6):7669–7675. doi: 10.3892/ol.2017.7219 . Cormier B, Rozenholc AT, Gotlieb W, Plante M, Giede C; Communities of Practice (CoP) Group of Society of Gynecologic Oncology of Canada (GOC). Sentinel lymph node procedure in endometrial cancer: A systematic review and proposal for standardization of future research. Gynecol Oncol. 2015;138(2):478–85. doi: 10.1016/j.ygyno.2015.05.039 . How J, Gotlieb WH, Press JZ, Abitbol J, Pelmus M, Ferenczy A, Probst S, Gotlieb R, Brin S, Lau S. Comparing indocyanine green, technetium, and blue dye for sentinel lymph node mapping in endometrial cancer. Gynecol Oncol. 2015;137(3):436–42. doi: 10.1016/j.ygyno.2015.04.004 . Tong M, Guo W, Gao W. Use of Fluorescence Imaging in Combination with Patent Blue Dye versus Patent Blue Dye Alone in Sentinel Lymph Node Biopsy in Breast Cancer. J Breast Cancer. 2014;17(3):250–5. doi: 10.4048/jbc.2014.17.3.250 . Frumovitz M, Plante M, Lee PS, Sandadi S, Lilja JF, Escobar PF, Gien LT, Urbauer DL, Abu-Rustum NR. Near-infrared fluorescence for detection of sentinel lymph nodes in women with cervical and uterine cancers (FILM): a randomised, phase 3, multicentre, non-inferiority trial. Lancet Oncol. 2018;19(10):1394–1403. doi: 10.1016/S1470-2045(18)30448-0 . Sahbai S, Taran FA, Fiz F, Staebler A, Becker S, Solomayer E, Wallwiener D, la Fougère C, Brucker S, Dittmann H. Pericervical Injection of 99mTc-Nanocolloid Is Superior to Peritumoral Injection for Sentinel Lymph Node Detection of Endometrial Cancer in SPECT/CT. Clin Nucl Med. 2016;41(12):927–932. doi: 10.1097/RLU.0000000000001414 . Szatkowski W, Pniewska K, Blecharz P, Nowak-Jasrząb M, Ryś J, Banaś T, Pacholczak-Madej R, Krzywonos E, Rawojć K, Kisielewicz K. 18-Hour Planar Scintigraphy Versus SPECT/CT for Sentinel Lymph Node Detection in Early-Stage Endometrial Cancer. Preprints 2025, 2025080651. https://doi.org/10.20944/preprints202508.0651.v1 Khoury-Collado F, Glaser GE, Zivanovic O, Sonoda Y, Levine DA, Chi DS, Gemignani ML, Barakat RR, Abu-Rustum NR. Improving sentinel lymph node detection rates in endometrial cancer: how many cases are needed? Gynecol Oncol. 2009;115(3):453–5. doi: 10.1016/j.ygyno.2009.08.026 . Tucker K, Staley SA, Gehrig PA, Soper JT, Boggess JF, Ivanova A, Rossi E. Defining the learning curve for successful staging with sentinel lymph node biopsy for endometrial cancer among surgeons at an academic institution. Int J Gynecol Cancer. 2020;30(3):346–351. doi: 10.1136/ijgc-2019-000942 . Abu-Rustum NR, Gomez JD, Alektiar KM, Soslow RA, Hensley ML, Leitao MM Jr, Gardner GJ, Sonoda Y, Chi DS, Barakat RR. The incidence of isolated paraaortic nodal metastasis in surgically staged endometrial cancer patients with negative pelvic lymph nodes. Gynecol Oncol. 2009;115(2):236–8. doi: 10.1016/j.ygyno.2009.07.016 . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7419838","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":504896222,"identity":"3beb2205-93c6-4b93-a575-9b4552049a34","order_by":0,"name":"Wiktor Szatkowski","email":"data:image/png;base64,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","orcid":"","institution":"Maria Skłodowska-Curie National Research Institute","correspondingAuthor":true,"prefix":"","firstName":"Wiktor","middleName":"","lastName":"Szatkowski","suffix":""},{"id":504896223,"identity":"a1847781-557e-4223-a0dc-9a0055c80bcd","order_by":1,"name":"Karolina Pniewska","email":"","orcid":"","institution":"Maria Skłodowska-Curie National Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Karolina","middleName":"","lastName":"Pniewska","suffix":""},{"id":504896224,"identity":"25777e68-cc69-4830-8602-420c317022de","order_by":2,"name":"Małgorzata Nowak-Jastrząb","email":"","orcid":"","institution":"Maria Skłodowska-Curie National Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Małgorzata","middleName":"","lastName":"Nowak-Jastrząb","suffix":""},{"id":504896225,"identity":"a8e1c229-707d-4524-b601-6493d72f2bbf","order_by":3,"name":"Kamil Kisielewicz","email":"","orcid":"","institution":"Maria Sklodowska-Curie National Research Institute of Oncology","correspondingAuthor":false,"prefix":"","firstName":"Kamil","middleName":"","lastName":"Kisielewicz","suffix":""},{"id":504896226,"identity":"7e5fd2b3-4967-4910-97a2-bff2396bfd80","order_by":4,"name":"Janusz Ryś","email":"","orcid":"","institution":"Maria Skłodowska-Curie National Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Janusz","middleName":"","lastName":"Ryś","suffix":""},{"id":504896227,"identity":"0522772f-89de-4bdf-8de0-5c0a559bee7a","order_by":5,"name":"Tomasz Banaś","email":"","orcid":"","institution":"Maria Skłodowska-Curie National Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Tomasz","middleName":"","lastName":"Banaś","suffix":""},{"id":504896228,"identity":"b211be4c-1ee7-4992-88d9-a7f028dce5c1","order_by":6,"name":"Paweł Blecharz","email":"","orcid":"","institution":"Maria Skłodowska-Curie National Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Paweł","middleName":"","lastName":"Blecharz","suffix":""}],"badges":[],"createdAt":"2025-08-20 17:53:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7419838/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7419838/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89993760,"identity":"04c2d5d2-8c95-45db-b526-155598b47f32","added_by":"auto","created_at":"2025-08-27 07:46:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":55320,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDistribution of SLNs and Metastatic SLNs by Anatomical Location\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePercentages in the 'SLNs detected' category refer to the proportion of all SLNs identified (n = 526). Percentages in the 'Metastatic SLNs' category refer to the proportion of all metastatic SLNs (n = 41) detected in 34 patients (27 with unilateral and 7 with bilateral metastases). Data were obtained from patients with endometrial cancer or complex atypical hyperplasia undergoing SLN mapping using Tc99m, indocyanine green (ICG), Patent Blue, or their combinations.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7419838/v1/54d1f975a14691dd9216e41d.png"},{"id":92921855,"identity":"5c16de05-5d61-4f0d-9ad3-6e834cbd97b4","added_by":"auto","created_at":"2025-10-07 07:09:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":867917,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7419838/v1/a66c520a-307f-4bed-9b7c-db41c28665ca.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Variability in Sentinel Lymph Node Locations in Endometrial Cancer: A Single-Center Study and Literature Review","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eEndometrial cancer is the most common gynecological malignancy in developed countries [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Sentinel lymph node biopsy (SLNB) is now widely accepted as an alternative to systematic pelvic lymphadenectomy, reducing surgical morbidity while maintaining high diagnostic accuracy [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The key element of this procedure is the identification of sentinel lymph nodes (SLNs), which are the first nodes to receive lymphatic drainage from the primary tumor. The incidence of lymph node metastases is approximately 20% in high-risk patients and 3\u0026ndash;9% in low-risk patients [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePrevious studies have demonstrated considerable variability in the anatomical location of SLNs in endometrial cancer [\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. This heterogeneity may result from multiple factors, including disease stage, tracer injection site and technique, tracer type, patient characteristics (e.g., BMI, histologic subtype), and surgeon experience [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Importantly, SLNB has been shown to be oncologically safe even in high-risk subgroups, such as patients with serous histology [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], deep myometrial invasion [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], or carcinosarcoma [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Compared with systematic lymphadenectomy, SLNB does not compromise recurrence-free or overall survival, while significantly reducing the risk of lymphedema and improving physical function and quality of life [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eMeta-analyses confirm that SLNB is an effective and less invasive alternative to complete lymphadenectomy, particularly when complemented by side-specific lymphadenectomy in cases of mapping failure [\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. This approach reduces the risk of both undertreatment and overtreatment, which remain important challenges in clinical practice [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Large prospective trials, including SENTI-ENDO [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], FIRES [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], and SHREC [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], have validated the diagnostic performance of SLNB, demonstrating high detection rates and low false-negative rates. Currently, cervical tracer injection is preferred, as it ensures higher bilateral detection and lower rates of technical failure [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAccording to NCCN guidelines, the effectiveness and safety of SLNB depend on adherence to a structured algorithm, which includes side-specific lymphadenectomy in the event of failed mapping and the removal of all suspicious lymph nodes regardless of SLN visualization [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Similarly, the ESGO\u0026ndash;ESTRO\u0026ndash;ESP [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], ESMO [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], and NCCN [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] guidelines recognize SLNB as a reliable method for lymph node assessment in patients with low-, intermediate-, and selected high-risk endometrial cancer.\u003c/p\u003e\u003cp\u003eA better understanding of SLN location variability is essential to optimize mapping efficacy and ensure accurate disease staging. The aim of this study was to analyze SLN locations in a single-center cohort of patients with endometrial cancer and to compare the findings with published literature. This comparison enables evaluation of the anatomical diversity of SLNs and exploration of potential reasons for discrepancies, including anatomical, technical, and clinical factors influencing mapping success.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Study Design and Setting\u003c/h2\u003e\u003cp\u003eThis retrospective cohort study was conducted at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland, between December 2016 and April 2025. Patients with endometrial cancer (EC) preoperatively classified as FIGO stage I\u0026ndash;II (2009 classification) based on clinical and imaging assessments [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] and who underwent SLN mapping were included. The study protocol was approved by the Ethics Committee of the National Research Institute of Oncology (approval no. 10/2025). All data were anonymized, and informed consent was obtained from patients in accordance with ethical guidelines.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Inclusion and Exclusion Criteria\u003c/h2\u003e\u003cp\u003eEligible patients had histologically confirmed endometrial cancer (FIGO stages IA\u0026ndash;IVB), received no neoadjuvant therapy, and had complete clinical and pathological data. Exclusion criteria included age below 18 or above 85 years and contraindications to surgical treatment. Of 306 patients initially screened for SLN mapping, 14 were excluded due to incomplete clinical data or advanced non-endometrial malignancies, resulting in a final cohort of 292 patients.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Sentinel Lymph Node Identification Procedure\u003c/h2\u003e\u003cp\u003eSurgical staging included total hysterectomy, bilateral salpingo-oophorectomy, and SLN mapping, performed via laparoscopy (n\u0026thinsp;=\u0026thinsp;242) or laparotomy (n\u0026thinsp;=\u0026thinsp;50) based on clinical indications (e.g., tumor size, BMI, comorbidities). SLN detection utilized technetium-99m (Tc99m), indocyanine green (ICG), Patent-Blue, or their combinations (primarily Tc99m with ICG), adapted from Szatkowski et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.3.1. Radioactive Tracer Administration (Tc99m)\u003c/h2\u003e\u003cp\u003eTechnetium-99m-labeled human albumin colloid (NanoColl, GE Healthcare, Chicago, IL, USA) was injected into the cervical stroma at the 3 and 9 o\u0026rsquo;clock positions, equally divided between superficial (2\u0026ndash;3 mm) and deep (10\u0026ndash;15 mm) layers using 21G needles. Two protocols were used: a short protocol (40 MBq, same-day surgery) for logistical feasibility and a long protocol (120 MBq, day before surgery) for enhanced tracer uptake. The Mediso AnyScan gamma camera (Mediso, Budapest, Hungary) facilitated preoperative and intraoperative SLN localization.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.3.2. Dye Administration\u003c/h2\u003e\u003cp\u003eTwo dyes were administered, either alone or in combination with Tc99m: (1) indocyanine green (ICG), 0.5 mL (1.25 mg) diluted in 5 mL sterile water, injected at the same cervical positions; (2) Patent Blue, 2 mL in total (1 mL per site). Dyes were injected 15\u0026ndash;30 min before surgery. Tc99m was used in all cases as the primary tracer. If preoperative scintigraphy showed incomplete or unilateral SLN detection, ICG or Patent Blue was added intraoperatively. ICG was applied whenever fluorescence imaging equipment was available.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\u003ch2\u003e2.3.3. Sentinel Lymph Node Identification\u003c/h2\u003e\u003cp\u003eSLNs were detected intraoperatively using a gamma probe (Gamma Finder 2, World of Medicine, Berlin, Germany) for Tc99m and a laparoscopic fluorescence imaging system (Visionsense 3DHD and IR Fluorescence V, Medtronic, Dublin, Ireland) for ICG and Patent Blue. SLNs were classified into obturator, external iliac, internal iliac, common iliac, para-aortic, parametrial, and presacral regions. All excised SLNs were verified ex vivo with the gamma probe. In laparotomy cases, tracer-based detection was supplemented by visual and manual inspection.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Histopathological Examination\u003c/h2\u003e\u003cp\u003eExcised sentinel lymph nodes (SLNs) were fixed in 10% formalin, sliced at 2 mm intervals, and stained with hematoxylin and eosin (H\u0026amp;E). Ultrastaging was performed using serial sectioning and immunohistochemistry for cytokeratins to detect isolated tumor cells (ITC), micrometastases (MM), and macrometastases (MAC).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Statistical Analysis\u003c/h2\u003e\u003cp\u003eData were analyzed using IBM SPSS Statistics v25.0. Qualitative variables, including SLN detection rates and anatomical locations, were summarized as frequencies (n) and percentages (%). Detection rates across tracer techniques were compared using the chi-squared test or Fisher\u0026rsquo;s exact test, with a two-tailed p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 considered statistically significant. Odds ratios (OR) with 95% confidence intervals (CI) were calculated to assess the likelihood of metastatic involvement in specific SLN locations. Quantitative variables (e.g., age, number of SLNs) were analyzed using t-tests or Mann-Whitney U tests as appropriate.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e2.6. SLN Evaluation Parameters\u003c/h2\u003e\u003cp\u003eThe following metrics were evaluated:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eBilateral detection rate (BDR): Percentage of patients with SLNs identified on both pelvic sides.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eUnilateral detection rate: Percentage of patients with SLNs identified on one pelvic side.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePara-aortic only detection: Percentage of patients with SLNs identified solely in the para-aortic region.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eNon-detection rate: Percentage of patients with no SLNs identified.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eNumber of SLNs per patient: Average number of SLNs detected per procedure.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMetastatic involvement rate: Percentage of patients with metastatic SLNs.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Patient Characteristics\u003c/h2\u003e\u003cp\u003eA total of 292 patients were included, with a median age of 68,2 years (range: 37\u0026ndash;84) and a median BMI of 31,1 kg/m\u0026sup2; (range: 19\u0026ndash;53) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.). The majority had endometrioid histology (80,8%), most commonly Grade 1 (39,7%) or Grade 2 (32,9%). Serous and clear-cell carcinomas accounted for 8,2% and 5,5% of cases, respectively, and 12 patients (4,1%) had complex atypical hyperplasia. According to the 2009 FIGO staging system, stage IA (35,9%) and IB (30,8%) were predominant, with advanced stages (II: 14,7%, IIIA\u0026ndash;C2: 14,0%, IVB: 0,3%) identified post-surgically. Surgical treatment was performed via laparoscopy (82,9%) or laparotomy (17,1%).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.2. SLN Mapping Protocols and Detection Rates\u003c/h2\u003e\u003cp\u003eMapping protocols are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Tc99m alone was the most frequent approach (38,3%), followed by ICG alone (37,0%) in selected cases due to logistical constraints, Tc99m\u0026thinsp;+\u0026thinsp;Patent Blue (16,4%), and Tc99m\u0026thinsp;+\u0026thinsp;ICG (8,2%). Tc99m was the initial tracer in most cases, with additional tracers applied intraoperatively for incomplete preoperative scintigraphy mapping. The overall bilateral detection rate was 87,0% (254/292 patients), unilateral detection occurred in 12,0% (35/292), and no SLN was identified in 1,0% (3/292). The mean number of SLNs per patient was 1,8 (median: 1,9; range: 0\u0026ndash;4).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Anatomical Distribution and Metastatic Involvement\u003c/h2\u003e\u003cp\u003eA total of 526 SLNs were identified across 292 patients (Table\u0026nbsp;3, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The most frequent anatomical locations were the obturator region (48,7%), internal iliac region (25,1%), external iliac (16,0%), and common iliac (7,2%) regions. Para-aortic (1,5%), presacral (1,1%), and parametrial (0,4%) nodes were rare. Metastases were detected in 41 SLNs (7,8% of all SLNs) from 34 patients (11,6% of the cohort), including 27 with unilateral metastases (1 SLN each) and 7 with bilateral metastases (2 SLNs each). The most frequent metastatic sites were the obturator region (17 SLNs, 41,5%), internal iliac nodes (7 SLNs, 17,1%), and external iliac nodes (6 SLNs, 14,6%), consistent with SHREC [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] and FIRES [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] reporting 95\u0026ndash;98% of SLN metastases in pelvic regions. Para-aortic SLNs (8 SLNs, 1,5%) showed a significantly higher likelihood of metastatic involvement (OR\u0026thinsp;=\u0026thinsp;13,00, 95% CI: 3,13\u0026ndash;54,02, p\u0026thinsp;=\u0026thinsp;0,0018). Most metastases were macrometastases (MAC, 32/41, 78,0%), with a predominance in the obturator region (15/17, 88,2%) and external iliac nodes (5/6, 83,3%). MAC were 3,09 times more likely in the obturator region compared to low-volume metastatic disease (LVMD; isolated tumor cells\u0026thinsp;+\u0026thinsp;micrometastases) when contrasted with other locations (OR\u0026thinsp;=\u0026thinsp;3,09, 95% CI: 0,55\u0026ndash;17,24, p\u0026thinsp;=\u0026thinsp;0,66, not statistically significant). The distribution of metastasis types is presented in Table\u0026nbsp;3. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the proportional distribution of SLNs and metastatic SLNs by anatomical location, with percentages in the \u0026ldquo;SLNs detected\u0026rdquo; category referring to all SLNs (n\u0026thinsp;=\u0026thinsp;526) and in the \u0026ldquo;Metastatic SLNs\u0026rdquo; category referring to metastatic SLNs (n\u0026thinsp;=\u0026thinsp;41) in 34 patients.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eClinical-Pathological Features and Mapping Outcomes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristics\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003en (%) or median (range)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePatients, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e292 (100)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emedian: 68.2 (range: 37\u0026ndash;84)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m\u0026sup2;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emedian: 31.1 (range: 19\u0026ndash;53)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHistology, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Complex atypical hyperplasia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e12 (4.1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Endometrioid Grade 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e116 (39.7)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Endometrioid Grade 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e96 (32.9)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Endometrioid Grade 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24 (8.2)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Serous\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24 (8.2)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Clear-cell\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (5.5)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Other\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (1.4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStage (2009 FIGO), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; IA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e105 (35.9)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; IB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e90 (30.8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e43 (14.7)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; IIIA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (2.4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; IIIC1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e31 (10.6)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; IIIC2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (1.0)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; IVB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (0.3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of SLNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emean 1.8 (median: 1.9, range: 0\u0026ndash;4)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSurgical approach, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Laparoscopy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e242 (82.9)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026ndash; Laparotomy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e50 (17.1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eNotes: Percentages may not sum to 100,0% due to rounding. Data collected from the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland (2016\u0026ndash;2025). Advanced stages (II\u0026ndash;IVB) were identified post-surgically.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMapping protocols and their application in the study cohort\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMapping protocol\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003en patients (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eApplication strategy in this study\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTc99m alone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e112 (38.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eStandard initial protocol; performed in all cases as the first step with preoperative planar scintigraphy. Proceeded directly to surgery if bilateral SLN visualization was achieved.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTc99m\u0026thinsp;+\u0026thinsp;ICG\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e24 (8.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAdded intraoperatively when preoperative Tc99m mapping was incomplete (unilateral or no SLN visualized) or when intraoperative conditions favored fluorescence imaging; choice also influenced by equipment availability.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTc99m\u0026thinsp;+\u0026thinsp;Patent Blue\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e48 (16.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAlternative complementary method used in cases of incomplete Tc99m mapping, selected based on surgeon\u0026rsquo;s discretion, patient factors, or technical considerations.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eICG alone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e108 (37.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eUsed in selected cases when Tc99m was not administered, mainly due to logistical or technical reasons, while ensuring full adherence to the mapping algorithm.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ePercentages may not sum to 100% due to rounding.\u003c/p\u003e\u003cp\u003eDetection outcomes:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eBilateral detection: 254/292 (87.0%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eUnilateral detection: 35/292 (12.0%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eNo SLN detected: 3/292 (1.0%)\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eNotes: Tc99m\u0026thinsp;=\u0026thinsp;technetium-99m; ICG\u0026thinsp;=\u0026thinsp;indocyanine green. Consistent with widespread international use, ICG was broadly applied in our cohort whenever fluorescence imaging was available, whereas Tc99m remained the initial tracer in all cases. Additional tracers were applied intraoperatively according to predefined criteria when preoperative scintigraphy showed incomplete bilateral SLN detection.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 3. Sentinel Lymph Node Characteristics in Endometrial Cancer\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"579\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eLocation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003eSLNs detected, n (% of all SLNs)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eSLNs with metastases, n (% of all with metastases)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003eITC, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003eMM, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003eMAC, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eInternal iliac\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e132 (25.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e6 (14.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e1 (16.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0 \u0026nbsp; \u0026nbsp; (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e5 (83.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eObturator\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e256 (48.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e17 (41.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e2 (11.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e15 (88.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eCommon iliac\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e38 (7.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e5 (12.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e2 (40.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e3 (60.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eExternal iliac\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e84 (16.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e7 (17.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e1 (14.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e1 (14.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e5 (71.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003ePara-aortic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e8 (1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e4 (9.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e2 (50.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0 \u0026nbsp; \u0026nbsp; (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e2 (50.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eParametrial\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e2 (0.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0 \u0026nbsp; \u0026nbsp; (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003ePresacral\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e6 (1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e2 (4.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e2 (100.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e526 (100.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e41 (100.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e4 (9.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e5 (12.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e32 (78.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAbbreviations: SLN, sentinel lymph node; ITC, isolated tumor cells; MM, micrometastases; MAC, macrometastases.\u003c/p\u003e\u003c/div\u003e\n\u003cp\u003e\u003cstrong\u003eNotes\u003c/strong\u003e: Data from 292 patients with endometrial cancer (FIGO IA\u0026ndash;IVB confirmed histologically, preoperative FIGO I\u0026ndash;II) or complex atypical hyperplasia (4,1%, 12 patients), treated at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland (2016\u0026ndash;2025). A total of 526 SLNs were detected using Tc99m, indocyanine green (ICG), Patent Blue, or their combinations. Mean number of SLNs per patient: 1,8 (median: 1,9, range: 0\u0026ndash;4). Percentages in the \u0026ldquo;SLNs detected\u0026rdquo; column refer to the total number of SLNs (526). Percentages in the \u0026ldquo;SLNs with metastases\u0026rdquo; column refer to 41 SLNs with metastases in 34 patients (27 with unilateral metastases, 1 SLN each; 7 with bilateral metastases, 2 SLNs each). Percentages in the ITC, MM, and MAC columns refer to metastatic SLNs in each location. Percentages may not sum to 100,0% due to rounding.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003e4.1. Anatomical variability of SLN localization\u003c/p\u003e\n\u003cp\u003eIn our study, 526 sentinel lymph nodes (SLNs) were identified in 292 patients with endometrial cancer or atypical endometrial hyperplasia (Table 3, Fig. 1). The most frequent sites were the obturator fossa (48.7%), internal iliac (25.1%), external iliac (16.0%), and common iliac (7.2%) regions. Less frequent locations included para-aortic (1.5%), presacral (1.1%), and parametrial (0.4%) nodes.\u003c/p\u003e\n\u003cp\u003eMetastases were detected in 41 SLNs in 34 patients (11.6% of the cohort), including seven bilateral cases. They were most commonly located in the obturator fossa (41.5%), along the internal iliac (17.1%) and external iliac arteries (14.6%), consistent with previous observations that 95\u0026ndash;98% of SLN metastases are located within the pelvis [10]. Although para-aortic nodes accounted for only 1.5% of all SLNs, the risk of metastasis was significantly higher in this region (OR = 13.00; 95% CI: 3.13\u0026ndash;54.02; p = 0.0018).\u003c/p\u003e\n\u003cp\u003eMost metastases were macrometastases (78.0%), particularly in the obturator region (88.2%). The relatively low prevalence of low-volume disease (LVMD: ITC + MM; 22.0%) compared with reports of up to 50% [28] may reflect differences in ultrastaging protocols or cohort characteristics. While the prognostic significance of macro- and micrometastases is well established, the clinical role of ITCs remains unclear [29,30]. Ongoing prospective studies (ALICE, SNEC [31]) may help to define their impact.\u003c/p\u003e\n\u003cp\u003e4.2. Impact of injection technique and surgical approach on SLN localization\u003c/p\u003e\n\u003cp\u003eThe site of injection and surgical technique have a significant influence on SLN localization [32,33]. In our cohort, which included both laparoscopic and open procedures, SLNs were most frequently identified in the obturator fossa (48.7%) and along the internal iliac artery (25.1%). These findings are in line with FIRES [9], How et al. [7], and L\u0026uuml;hrs et al. [10].\u003c/p\u003e\n\u003cp\u003eHuber et al. [11], using the transvaginal vNOTES approach, reported a markedly higher proportion of obturator nodes (81.5%), most likely attributable to the surgical technique itself. Anatomical variability is also influenced by individual lymphatic drainage pathways. Kimmig et al. [34] and Persson et al. [23] described three main lymphatic routes from the uterus: external iliac, obturator, and para-aortic.\u003c/p\u003e\n\u003cp\u003eIn our study, cervical injections were used, which preferentially highlight pelvic and obturator drainage pathways compared with fundal injections [35]. The choice of tracers (Tc99m, ICG, Patent Blue [7]) also affected the distribution of SLNs. Rare sites, such as para-aortic or presacral nodes, were observed at frequencies similar to previous reports [7,10,32].\u003c/p\u003e\n\u003cp\u003e4.3. Detection rates and tracer performance\u003c/p\u003e\n\u003cp\u003eThe overall SLN detection rate was 98.9%, with bilateral detection in 87.0%. These figures are slightly lower than in SHREC (100% and 91.9% [23]), likely due to population differences and less frequent use of reinjection protocols in our cohort. Detection rates improved in later years with increased use of tracer combinations (ICG + Tc99m in 8.2% and ICG + Patent Blue in 16.4%) and reinjection of ICG, consistent with SHREC recommendations [23].\u003c/p\u003e\n\u003cp\u003eICG demonstrates higher sensitivity than blue dyes [8,24,25]. In the study by Ehrisman et al. [36], the detection rate of metastatic SLNs was 90% with ICG versus 75% with Patent Blue (p = 0.05). Limitations of blue dyes include rapid washout, reduced penetration in obese patients, and diffusion into parametrial tissues [37-39]. Despite its diagnostic superiority, ICG carries the risk of misidentifying secondary nodes, leading to removal of superficial non-sentinel nodes instead of true SLNs [40]. Additional pitfalls such as \u0026ldquo;empty nodal packets\u0026rdquo; (5\u0026ndash;6% of cases) [40] and the \u0026ldquo;glow effect\u0026rdquo; during delayed assessment [33,40-41] increase the risk of false mapping. For this reason, mapping is recommended at the beginning of the procedure in a clean surgical field.\u003c/p\u003e\n\u003cp\u003eIn our study, the obturator fossa was the dominant site of metastatic SLNs (41.5%, 17/41), confirming the observations of L\u0026uuml;hrs et al. (48.6% [10]). Clinically, this highlights the need for meticulous exploration of the obturator region, despite technical challenges. In obese patients, ICG fluorescence may be limited, while in older patients tortuous vessels along the external iliac artery hinder access. In such cases, Tc99m, alone or combined with ICG, enabled more effective SLN detection.\u003c/p\u003e\n\u003cp\u003eThe advantage of Tc99m lies in its physicochemical properties: larger particle size (human albumin colloid 50\u0026ndash;200 nm [19]) ensures longer nodal retention and minimizes diffusion to secondary nodes [42,43], effectively preventing removal of second-tier nodes seen with ICG. In our previous study using Tc99m alone, the mean number of nodes per SLN region was 1.4 [44], compared with 1.8 in the present cohort with multiple tracer combinations. Fewer nodes suggest higher selectivity of Tc99m, while the combination of ICG + Tc99m improved mapping efficacy in anatomically challenging cases (obesity, deep obturator nodes).\u003c/p\u003e\n\u003cp\u003e4.4. Standardization and surgical algorithms\u003c/p\u003e\n\u003cp\u003eDifferences in SLN detection efficacy across studies may reflect variations in injection protocols, tracer types and doses, and surgical techniques. According to NCCN and ESGO-ESTRO-ESP guidelines [2,3], the SLN algorithm should include unilateral lymphadenectomy in cases of failed mapping and mandatory removal of suspicious nodes. These procedures were followed in our study, minimizing the risk of false-negative results, though para-aortic metastases may still be missed.\u003c/p\u003e\n\u003cp\u003eOur findings demonstrated high sensitivity and negative predictive value of SLN biopsy, consistent with FIRES [9] and SENTI-ENDO [22]. The lower bilateral detection rate (87.0%) compared with SHREC (91.9% [23]) may partly reflect a learning-curve effect, as emphasized by Khoury-Collado et al. [45] and Tucker [46], who reported improved detection after \u0026gt;30\u0026ndash;40 procedures. A similar trend of increasing detection efficacy was observed in our cohort over time.\u003c/p\u003e\n\u003cp\u003eThe two-step mapping strategy described by Kim et al. [35] could improve the detection of rare para-aortic SLNs (1.5% in our study), which in some cases represent the only site of metastasis (0.5\u0026ndash;3.8% [47]). The lack of standardization in tracer type, injection technique, and ultrastaging protocols hampers comparability across studies and may contribute to discrepancies in the reported detection of rare or micrometastatic disease [39].\u003c/p\u003e\n\u003cp\u003e4.5. Study limitations\u003c/p\u003e\n\u003cp\u003eOur study has several limitations. First, it was conducted in a single institution, limiting the generalizability of results. Second, different surgical approaches (laparotomy, laparoscopy) and tracer combinations were used during the study period, which may have influenced outcomes. Third, reinjection of ICG and standardized two-step mapping protocols were not routinely performed, potentially underestimating rare SLN locations. Finally, we did not analyze in detail the effect of the surgical learning curve or clinical factors such as obesity or prior treatments.\u003c/p\u003e\n\u003cp\u003e4.6. Future perspectives\u003c/p\u003e\n\u003cp\u003eFuture studies should focus on multicenter analyses with harmonized SLN protocols, including standardized tracer doses and types, injection techniques, and uniform ultrastaging assessment. Particular attention should be given to rare SLN localizations (paraaortic, presacral), which, although infrequent, may carry clinical significance. Another important direction is evaluating the clinical impact of low-volume metastases (ITC, MM) on treatment decisions. Comparative analyses of tracer combinations in high-risk groups (obesity, non-endometrioid histology) and integration of preoperative imaging (SPECT/CT, two-step protocols) and digital tools (AI) may further enhance the accuracy and reproducibility of SLN detection.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eSentinel lymph node biopsy is an effective and safe method for lymph node assessment in endometrial cancer, allowing a reduction in the extent of lymphadenectomy while maintaining high diagnostic sensitivity. In our cohort, the obturator region was the most frequent site of both overall and metastatic SLNs, emphasizing the need for careful exploration of this area despite technical challenges. The use of combined tracers (Tc99m\u0026thinsp;+\u0026thinsp;ICG/Patent Blue) increased mapping precision, reduced the risk of \u0026ldquo;empty\u0026rdquo; nodal packets, and improved metastasis detection. Further standardization of injection protocols, dose optimization, and the incorporation of preoperative imaging may enhance detection rates, particularly in rare localizations such as para-aortic nodes.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eSLNB : Sentinel lymph node biopsy\u003c/p\u003e\n\u003cp\u003eEC: endometrial cancer\u003c/p\u003e\n\u003cp\u003eSLN: sentinel lymph node\u003c/p\u003e\n\u003cp\u003eTc99m: technetium-99m \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eICG : indocyanine green\u003c/p\u003e\n\u003cp\u003eNCCN: National Comprehensive Cancer Network\u003c/p\u003e\n\u003cp\u003eESGO-ESTRO-ESP:\u0026nbsp;European Society of Gynaecological Oncology - European Society for Radiotherapy and Oncology - European Society of Pathology\u003c/p\u003e\n\u003cp\u003eESMO: European Society for Medical Oncology\u003c/p\u003e\n\u003cp\u003eBMI: body mass index\u003c/p\u003e\n\u003cp\u003eH\u0026amp;E : hematoxylin and eosin\u003c/p\u003e\n\u003cp\u003eITC : detect isolated tumor cells \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMM: micrometastases\u003c/p\u003e\n\u003cp\u003eMAC: macrometastases\u003c/p\u003e\n\u003cp\u003eBDR: \u0026nbsp; Bilateral detection rate\u003c/p\u003e\n\u003cp\u003eLVMD: low-volume metastatic disease\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003eConflicts of Interest\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflicts of interest.\u003c/p\u003e\n\u003cp\u003eEthics Approval\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch, Poland (Approval No. 10/2025), and was conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003eConsent to Participate\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from all participants.\u003c/p\u003e\n\u003cp\u003eConsent for Publication\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003eAvailability of Data and Materials\u003c/p\u003e\n\u003cp\u003eStatistical results reported in this article are publicly available. Access to raw patient-level data is restricted and may be obtained from the corresponding author upon reasonable request, subject to approval by the Ethics Committee of the Maria Sklodowska-Curie National Research Institute of Oncology.\u003c/p\u003e\n\u003cp\u003eAuthors\u0026rsquo; Contributions\u003c/p\u003e\n\u003cp\u003eStudy conception and design: WS,PB,TB.\u003c/p\u003e\n\u003cp\u003eMaterial preparation and data collection: WS,KP,KK,MNJ.\u003c/p\u003e\n\u003cp\u003eHistopathological evaluation: JR.\u003c/p\u003e\n\u003cp\u003eStatistical analysis: WS, KP.\u003c/p\u003e\n\u003cp\u003eFirst draft of the manuscript: WS.\u003c/p\u003e\n\u003cp\u003eCritical review and editing: KP, KK, MNJ,JR,TB and PB.\u003c/p\u003e\n\u003cp\u003eAll authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eAcknowledgements: None.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, Bray F. 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Gynecol Oncol. 2009;115(2):236\u0026ndash;8. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ygyno.2009.07.016\u003c/span\u003e\u003cspan address=\"10.1016/j.ygyno.2009.07.016\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"endometrial cancer, sentinel lymph node, mapping, technetium-99m, indocyanine green, lymphatic anatomy, tracer combinations, metastases","lastPublishedDoi":"10.21203/rs.3.rs-7419838/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7419838/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eSentinel lymph node biopsy (SLNB) has become a widely accepted alternative to systematic lymphadenectomy in endometrial cancer (EC), reducing surgical morbidity without compromising diagnostic accuracy. However, the anatomical variability of sentinel lymph node (SLN) locations remains insufficiently understood, with substantial differences reported across studies. This study analyzed SLN distribution in a large single-center cohort and compared the findings with published data.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eWe retrospectively analyzed 292 patients with EC treated at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch (2016\u0026ndash;2025). All underwent SLN mapping using technetium-99m (Tc99m), indocyanine green (ICG), Patent Blue, or their combinations. Bilateral detection failures were managed according to an established intraoperative algorithm. SLNs were classified anatomically, and outcomes were compared across mapping techniques. Histopathological assessment included ultrastaging.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eA total of 526 SLNs were identified (mean 1.8 per patient). The most common locations were the obturator (48.7%) and internal iliac (25.1%) regions. Bilateral detection was achieved in 87.0% of patients, unilateral in 12.0%, and no detection in 1.0%. Metastases were found in 41 SLNs (7.8%) from 34 patients (11.6%), most frequently in obturator (41.5%) and internal iliac (17.1%) nodes. The use of tracer combinations (ICG\u0026thinsp;+\u0026thinsp;Tc99m or Tc99m\u0026thinsp;+\u0026thinsp;Patent Blue) improved detection when preoperative Tc99m mapping was incomplete. Para-aortic SLNs were rare (1.5%) but carried a significantly higher risk of metastasis.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eSLNB is an effective and safe method for nodal assessment in EC, with the obturator and internal iliac regions being the most frequent SLN sites. Variability in SLN locations appears to depend on mapping technique, tracer type, and surgical access. Standardization of procedures and prospective comparative studies are essential to further optimize SLNB in gynecologic oncology.\u003c/p\u003e","manuscriptTitle":"Variability in Sentinel Lymph Node Locations in Endometrial Cancer: A Single-Center Study and Literature Review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-27 07:46:08","doi":"10.21203/rs.3.rs-7419838/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9e50a2a9-f611-4da4-955c-084ca45e4215","owner":[],"postedDate":"August 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-07T07:09:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-27 07:46:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7419838","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7419838","identity":"rs-7419838","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}