Incidentally Discovered Ovarian Cancer Combined With Obturator Nerve Schwannoma: A Rare Case Report

A rare coexistence of high-grade serous ovarian cancer and an obturator nerve schwannoma presented as a node-like pelvic sidewall mass. A 50-year-old woman had progressive abdominal distension, CA-125 1534 U/mL (reference range 0–35 U/mL), and computed tomography (CT) showing ovarian cancer with a left sidewall mass interpreted as nodal disease. After three cycles of paclitaxel–carboplatin, the ovarian disease regressed while the sidewall mass was unchanged. Because a percutaneous route was likely to traverse major vessels and open cytoreduction was planned, biopsy was deferred. At laparotomy, a well-circumscribed lesion centered on the obturator canal was dissected along the epineurial plane and intracapsularly enucleated, preserving the obturator nerve and its fascicles. Pathology showed schwannoma (spindle-cell fascicles with Verocay bodies; diffuse S-100 positivity; no epithelial markers). Posttreatment CT met the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 for complete response; the patient received maintenance olaparib plus bevacizumab and, at 32-month follow-up, had no evidence of recurrence with intact adductor function. This case suggests that, during ovarian cancer cytoreduction, a stable, well-circumscribed sidewall mass on CT—particularly along the obturator canal—should raise suspicion for a neurogenic tumor; when biopsy access is unsafe and open surgery is planned, nerve-sparing enucleation is an appropriate management option. Summary - During cytoreduction for ovarian cancer, a stable, well-circumscribed pelvic sidewall mass on CT—especially along the obturator canal—may be neurogenic rather than nodal. - When percutaneous access is unsafe and open surgery is planned, deferring biopsy and performing nerve-sparing enucleation can preserve adductor function with definitive diagnosis at pathology. 1 Introduction Obturator nerve schwannoma (ONS) is a rare benign peripheral nerve sheath tumor that arises along the pelvic sidewall and within the obturator canal [1]. Owing to this deep pelvic course—often near the adnexa—ONS is frequently mistaken for an adnexal lesion or pelvic nodal disease [2, 3]. It may be presented with pelvic pain or medial thigh paresthesia or be discovered incidentally [1, 4]. On magnetic resonance imaging (MRI), ONS is typically T1 hypointense and T2 hyperintense; the most specific clue to neural origin is demonstrable continuity of the mass with the obturator nerve on axial or coronal images [5]. Key differentials are metastatic or reactive lymphadenopathy [6], pedunculated subserosal leiomyoma [7], obturator hernia [8], and intraneural ganglion cyst [9]. Malignant peripheral nerve sheath tumor (MPNST) involving the obturator nerve is rare but should be considered when imaging shows infiltrative features or rapid enlargement are seen [10]. In cytoreductive surgery for advanced ovarian cancer, distinguishing a neurogenic pelvic sidewall mass from nodal metastasis guides operative planning—specifically, lymphadenectomy versus nerve-sparing enucleation—and has direct implications for postoperative adductor function [4]. We report a patient with high-grade serous ovarian cancer (HGSOC), and a pelvic sidewall mass interpreted as nodal metastasis on preoperative computed tomography (CT) that proved to be an ONS, and we outline imaging and operative considerations for nerve preservation during definitive oncologic surgery. 2 Case Presentation A 50-year-old woman presented in December 2021 with a 1-month history of progressive abdominal distension. She had no significant past medical history; her only prior surgery was tubal ligation 20 years earlier. Her obstetric history was gravida 2, para 2 (G2P2), with two term vaginal deliveries. There was no family history of ovarian or breast cancer. On examination, the abdomen was distended, and a large mixed cystic-solid mass was palpated, with its upper border at the level of the umbilicus and appearing contiguous with the uterus. On digital rectal (rectovaginal) examination, an approximately 8 cm mass was palpated in the rectouterine pouch (Douglas pouch); it had limited mobility and was non-tender. 3 Investigations and Management Baseline testing showed a markedly elevated CA-125 of 1534 U/mL (reference range 0–35 U/mL); other tumor markers (CEA, AFP, SCC antigen, CA19-9, NSE, CA15-3, HE4, hCG, and CA72-4) were within reference ranges. Contrast-enhanced CT demonstrated multiple mixed cystic-solid pelvic masses likely of ovarian origin, along with peritoneal and omental thickening consistent with carcinomatosis. A separate soft tissue mass along the left pelvic sidewall abutting the iliac vessels was interpreted as nodal metastasis (Figure 1). Image-guided biopsy of a pelvic mass showed adenocarcinoma consistent with high-grade serous carcinoma. Immunohistochemistry (IHC) demonstrated cytokeratin 7 (CK7)+, paired box 8 (PAX8)+, Wilms tumor 1 (WT1)+, aberrant (mutant-type) p53, estrogen receptor (ER) 80% (moderate–strong) positive, progesterone receptor (PR) weak/focal (~1%), Ki-67 ~30%, and negativity for cytokeratin 5/6 (CK5/6), podoplanin (D2-40), synaptophysin, chromogranin A, and CD56/NCAM; p16 was positive. For a left pelvic sidewall mass, the differential prioritized nodal metastasis, with alternatives of a neurogenic tumor—particularly an ONS/peripheral nerve sheath tumor—and, less likely, retroperitoneal sarcoma or an obturator hernia. The patient received three cycles of paclitaxel–carboplatin. CA-125 fell to 35.08 U/mL, approaching the normal range. Interval CT after chemotherapy showed that (1) multiple mixed cystic-solid pelvic nodules and masses decreased in size and number; (2) previously noted peritoneal and omental thickening markedly decreased, with near-resolution of ascites; and (3) the left pelvic sidewall mass abutting the iliac vessels—interpreted as nodal metastasis—was essentially unchanged compared with baseline. Overall response was stable disease per the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. In March 2022, open cytoreductive surgery was performed. An approximately 5 cm encapsulated solid mass was identified between the left common iliac artery and the psoas major muscle, in close association with the left obturator nerve (Figure 2A). The mass was completely enucleated with preservation of the nerve (Figure 2B–D). The patient recovered well without gait limitation, adductor weakness, or neuropathic pain. Postoperative pathology confirmed an ONS (Figure 3)—a spindle-cell tumor with nuclear palisading and diffuse, strong S-100 positivity—and germline testing identified a pathogenic variant in breast cancer gene 1 (BRCA1) associated with the patient's ovarian cancer. 4 Outcome and Follow-Up Postoperatively, the patient received five cycles of adjuvant paclitaxel–carboplatin plus bevacizumab. A posttreatment CT demonstrated no evidence of disease (Figure 4). Maintenance therapy with olaparib plus bevacizumab continued through September 2023. At the last follow-up in November 2024—32 months after surgery—CT showed no evidence of recurrence, and serum CA-125 remained within the normal range. 5 Discussion This report describes the uncommon coexistence of HGSOC and an ONS that mimicked pelvic nodal disease on preoperative imaging. The sidewall mass remained essentially unchanged after neoadjuvant paclitaxel–carboplatin despite a systemic response elsewhere. Intraoperative assessment therefore favored nerve-sparing enucleation, which preserved adductor function while complete cytoreduction was achieved. Similar masquerading presentations—particularly as adnexal or nodal pathology—have been reported in gynecologic settings when a mass abuts the obturator canal or the external iliac vessels [2, 11]. As far as we know, this is the first report of ovarian cancer combined with ONS; published cases typically describe pelvic/obturator schwannomas mimicking adnexal or nodal disease without coexisting ovarian malignancy [2, 11-13]. This case highlights the diagnostic complexity of retroperitoneal schwannomas, especially when they occur concurrently with ovarian cancer. From a diagnostic standpoint, the differential diagnosis for a female pelvic sidewall mass includes metastatic or reactive lymphadenopathy, pedunculated subserosal leiomyoma, obturator hernia, and neurogenic tumors (schwannoma, neurofibroma, perineurioma, and—rarely—MPNST) [6-9, 14]. Cross-sectional imaging of ONS typically shows a well-circumscribed solid or mixed cystic-solid lesion. On MRI, T1 hypointensity and T2 hyperintensity are common but not specific [5, 11, 15]. The most practical clue to neural origin is demonstrable continuity with the obturator nerve on axial or coronal sequences, repeatedly emphasized in pelvic schwannoma reports [2, 11, 15, 16]. Even with careful imaging, radiology alone seldom secures a definitive diagnosis. Image-guided core biopsy can be informative when results would alter management; however, for lesions abutting the iliac vessels—particularly small-volume tumors—needle biopsy can carry a nontrivial risk of vascular injury; when a safe, avascular trajectory cannot be confirmed by interventional radiology, intraoperative diagnosis during planned cytoreduction is reasonable. Conversely, if a safe, avascular trajectory exists and the result would change management, core biopsy by an experienced team after MDT review is reasonable [17-19]. Positron emission tomography/computed tomography (PET/CT) uptake is not a reliable discriminator between benign schwannoma and metastatic nodes, and diffusion-weighted imaging (DWI)/apparent diffusion coefficient (ADC) metrics are adjunctive rather than definitive. Given the radiologic–clinical discordance in our case (systemic response with a stable pelvic sidewall mass), we next summarize how the literature-based ONS misdiagnosis table informs operative planning. Table 1 synthesizes features of misdiagnosed ONS: (1) presentations most often mimic an adnexal mass or an “obturator lymph node” when the lesion lies in the pelvic sidewall corridor; (2) routine CT/MRI are frequently nonspecific, whereas the most useful clue is demonstrable continuity with the obturator nerve on thin-slice axial/coronal imaging or at surgery; (3) when an epineurial/perineurial plane is present, intracapsular, fascicle-sparing enucleation can preserve adductor function, while segmental resection is reserved for fascicles that are inseparable; and (4) PET/CT avidity and DWI hyperintensity are not specific for malignancy versus benign nerve-sheath tumors, and small sidewall lesions in patients with another pelvic malignancy are commonly interpreted as nodal disease. These observations align with Table 2, which contrasts location along the nerve course, presence of a capsule/epineurial plane, immunoprofiles (S-100/SOX10 vs. CK/PAX8/WT1), and the typical chemotherapy stability of benign lesions, thereby informing preoperative review and intraoperative decisions [2, 3, 6, 20-24]. | Author, year | Sex/age | Side & corridor | Size & pattern | Symptom | Initial diagnosis | Imaging key (neural continuity; modality) | Coexisting malignancy | Surgery (approach ± frozen) | Nerve management | Path/IHC | Outcome & follow-up | References | |---|---|---|---|---|---|---|---|---|---|---|---|---| | Scotto (1998) | F/66 | Right; pelvic sidewall–obturator corridor | 60 × 42 × 45 mm; mixed cystic-solid | Pelvic pain | Ovarian cystadenocarcinoma; enlarged right obturator lymph node | Imaging corridor clue; neural continuity appreciated at surgery | None | Laparoscopic exploration, followed by open pelvic tumor resection; frozen sections were not used | Obturator nerve transected inadvertently | Benign schwannoma; classic histology | No neurologic sequelae; 6-mo no recurrence | [20] | | Yi (2010) | F/31 | Left; retroperitoneal–obturator foramen (behind external iliac artery) | 8.8 × 5.3 × 5.1 cm; solid | No neurological symptoms were observed | Ovarian cyst vs. broad ligament fibroid | Neural continuity recognized intra-op; MRI/US nonspecific | None | Laparoscopic resection of a left obturator fossa tumor; frozen section benign | Fascicle-sparing capsular enucleation; nerve preserved | Benign schwannoma; S-100+ | No neurodeficit; 17-mo no recurrence | [3] | | Sasaki (2010) | M/58 | Left; obturator region | 16 × 14 mm; solid | No neurological symptoms were observed | Obturator lymph-node metastasis | Neural continuity recognized intra-op; CT/MRI: left obturator lymph node swelling; PET/CT uptake present | Bladder pTa + colon adenocarcinoma | Limited incision biopsy → enucleation; frozen sections were not used | Nerve preserved (capsular excision) | Benign schwannoma; Antoni A/B | No neurodeficit; 6-mo no recurrence | [6] | | De Sousa (2012) | M/58 | Left; obturator region, giant lesion | 75 × 85 × 100 mm; solid | Persistent pain and paraesthesia in the medial aspect of the left knee, along with a gait disturbance | Giant malignant lymph node | CT/MRI/US nonspecific; neural continuity not appreciated pre-op | High-risk prostate cancer | Open RRP + PLND + mass excision; frozen sections were not used | Obturator nerve transected inadvertently | Benign schwannoma; S-100+ | Mild adductor weakness; pain relief; NR follow-up | [21] | | Masahiro (2015) | F/71 | Left; obturator region | 15 mm; solid | No neurological symptoms were observed | Rectal lateral pelvic lymph-node metastasis | Neural continuity visible on sagittal MRI review; DWI high/PET/CT avid | Rectal cancer | Laparoscopic TPC with IPAA + left LPLN dissection; en bloc excision of an obturator nerve–contiguous mass (obturator nerve transected); frozen sections were not used | Segmental nerve resection (intra-op cut) | Benign schwannoma; S-100+ | Mild adductor weakness at 4-mo; 15-mo no recurrence | [22] | | Gleason (2017) | F/63 | Left; pelvic sidewall–obturator corridor | 4.5 × 2.5 × 1.5 cm; mixed cystic-solid | Worsening pelvic pain | Adnexal/ovarian malignancy | Neural continuity seen intra-op; MRI T1 low/T2 high, peripheral enhancement | None | Laparotomy with total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH-BSO) plus retroperitoneal pelvic sidewall mass excision; frozen sections were not used | Fascicle-sparing enucleation; nerve preserved | Benign schwannoma; S-100+ | Neurologic deficits and resolution of pelvic pain at 2-mo; 2-mo no recurrence | [2] | | Bai (2020) | F/58 | Right; obturator corridor (string-of-beads) | The largest was 4.0 × 3.0 cm and the smallest was 0.5 × 0.5 cm; cystic/gelatinous nodules | No neurological symptoms were observed | Adnexal mass | Continuity with obturator nerve confirmed intra-op; CT/US nonspecific | None | Laparoscopic BSO + hysteroscopic polypectomy; laparoscopic excision of multiple obturator-nerve nodules; frozen section benign | Fascicle-sparing removal; nerve preserved | Benign schwannoma; SOX10+ | Discharged POD5; no deficits; NR follow-up | [23] | | Shi (2024) | F/52 | Right; obturator fossa (blood supply from obturator artery) | 100 × 80 mm; mixed cystic-solid | Pelvic pain | Adnexal/ovarian or GI tumor | CT/US nonspecific; intra-op portions of the nerve were incorporated into—and inseparable from—the mass | None | Laparoscopic presacral/retroperitoneal mass resection; intraoperative frozen section: neurinoma without atypia | Segmental obturator nerve resection | Benign schwannoma; S-100+ | Transient adductor weakness → recovered by 6 mo; 15-mo NED; 58-mo phone FU OK | [24] | - Abbreviations: BSO, bilateral salpingo-oophorectomy; CT, computed tomography; DWI, diffusion-weighted imaging; FU, follow-up; IHC, immunohistochemistry; IPAA, ileal pouch-anal anastomosis; LPLN, lateral pelvic lymph nodes; mo, months; MRI, magnetic resonance imaging; NED, no evidence of disease; NR, not reported; PET/CT, positron emission tomography/computed tomography; PLND, pelvic lymph node dissection; POD, postoperative day; RRP, radical retropubic prostatectomy; TAH-BSO, total abdominal hysterectomy and bilateral salpingo-oophorectomy; TPC, total proctocolectomy; US, ultrasonography. | Domain | Feature | Obturator nerve schwannoma | Pelvic nodal metastasis | |---|---|---|---| | Imaging | Typical location | Pelvic sidewall/obturator canal; aligned with the obturator nerve course | Anatomic nodal stations (external/internal iliac chains, obturator fossa); not centered on a nerve | | Morphology | Well-circumscribed, ovoid; solid or mixed cystic-solid | Round/reniform node; central necrosis may appear in enlarged nodes | | | US (B-mode/Doppler) | Well-defined hypoechoic solid mass; posterior enhancement; peripheral or sparse internal flow; no fatty hilum; trackable along nerve with a high frequency probe | Oval/round hypoechoic node with cortical thickening and absent or effaced fatty hilum; peripheral or mixed hilar flow; necrotic nodes may appear cystic/heterogeneous | | | CT characteristics | Well-circumscribed soft tissue mass iso- to hypodense to muscle; homogeneous or mildly heterogeneous enhancement; preserves fat plane; centered on the obturator canal/along the obturator nerve trajectory | Enlarged nodes at nodal stations; short-axis enlargement (≥ 1 cm), irregular margins, central low attenuation/necrosis, rim enhancement; possible matted nodes or extranodal extension | | | MRI signal | T1 hypointense; T2 hyperintense; possible target/fascicular sign | Variable T1/T2; heterogeneity/necrosis in advanced disease | | | Continuity sign (MR neurography) | Continuity with the obturator nerve on axial/coronal sequences | No continuity with a nerve is demonstrable | | | DWI/ADC | Typically intermediate/high ADC (lower cellularity) | Often lower ADC (higher cellularity); overlap exists | | | Contrast enhancement | Homogeneous or peripheral/septal; capsular rim may be visible | Heterogeneous; necrotic nodes show peripheral rim | | | PET/CT | Uptake variable (SUV can be elevated in benign schwannoma) | Uptake commonly elevated | | | Interval change after chemotherapy and/or radiotherapy | Generally stable in size (benign lesions are nonresponsive to chemotherapy or radiotherapy) | Commonly decrease in size with effective chemotherapy and/or radiotherapy | | | Intraoperative | Capsule/plane of dissection | Intact capsule; epineurial/perineurial plane permits intracapsular enucleation | No true capsule; may adhere to fat/vessels; extranodal extension possible | | Relationship to nerve/vessels | Displaces/abuts obturator nerve without fascicular infiltration | No continuity with a nerve; may adhere to or encase vessels/soft tissue | | | Bleeding risk | Primarily from branches of the obturator venous plexus | During nodal basin dissection, bleeding may arise from vascular adhesions or extranodal extension | | | Histopathology | Architecture | Encapsulated; Antoni A/B areas with Verocay bodies | Nodal architecture effaced; sinus loss; extranodal extension may be present | | Immunophenotype | Diffuse strong S-100/SOX10 positive; CK/PAX8/WT1 negative | Matches primary carcinoma (e.g., serous carcinoma: CK/PAX8/WT1 positive) | | | Proliferation/necrosis | Ki-67 typically low; necrosis and brisk mitoses absent | Higher Ki-67; necrosis and extranodal spread may occur | | | Neurofilament (axonal distribution) | Axons displaced to a compressed peripheral rim | Axons not a defining feature; may be destroyed/entrapped by metastasis | | | Malignancy exclusion (MPNST pathway) | Retains diffuse S-100; lacks infiltrative borders/necrosis; H3K27me3 retained | Not applicable | - Note: Key sources: imaging misclassification & continuity sign [2, 11, 15, 16]; interval change after chemotherapy and/or radiotherapy [11, 25, 26]; PET/CT limitations [27]; nerve-sparing enucleation (open/laparoscopic/robotic) [2, 13, 28]; immunophenotype (S-100/SOX10 vs. CK/PAX8/WT1) [2, 11]; MPNST features & H3K27me3 [10, 14, 29]. - Abbreviations: ADC, apparent diffusion coefficient; CK, cytokeratin; CT, computed tomography; DWI, diffusion-weighted imaging; FDG, fluorodeoxyglucose; MPNST, malignant peripheral nerve sheath tumor; MRI, magnetic resonance imaging; PET/CT, positron emission tomography/computed tomography; US, ultrasonography. Because preoperative imaging poorly differentiates ONS from pelvic nodal metastasis, often leading to misdiagnosis—we summarize key distinctions across imaging, intraoperative findings, and histopathology (Table 2). In ovarian cancer pathways, discordance between systemic response and a stable pelvic sidewall lesion should prompt targeted MRI review for continuity with the obturator nerve. If continuity is demonstrated and open cytoreduction is already planned, intraoperative diagnosis with epineurial plane enucleation is reasonable, provided vascular control and nerve identification are secured. When fascicles are inseparable, limited segmental resection with tension-free neurorrhaphy may be required [22, 24]. Preoperative core biopsy is reserved for scenarios in which results would change management and a safe, avascular percutaneous trajectory can be confirmed by interventional radiology [30]. For primary cytoreduction in advanced HGSOC, the National Comprehensive Cancer Network (NCCN) Ovarian Cancer Guidelines (Version 3.2025) [30] generally favor an open approach to enable comprehensive assessment and complete resection when feasible. Minimally invasive cytoreduction is not standard in this setting; however, for a well-localized neurogenic tumor encountered during oncologic surgery, nerve-sparing enucleation can be performed safely under magnified visualization (selected laparoscopic/robotic reports) without compromising oncologic aims [13, 28]. As summarized in Table 2, an intact capsule and a clear epineurial/perineurial plane favor intracapsular enucleation with nerve preservation. Segmental resection with end-to-end neurorrhaphy or interposition conduit is occasionally necessary if the tumor cannot be separated from critical fascicles; nevertheless, most pelvic schwannomas—including ONS—are amenable to enucleation with preservation of adductor strength [3, 18, 24, 28]. Classic schwannomas are encapsulated and show alternating Antoni A/B areas, Verocay bodies, and diffuse S-100 positivity—as in our specimen. MPNST of the obturator nerve is rare. Concerning features include infiltrative margins, necrosis, brisk mitoses, and reduced or heterogeneous S-100 staining; a subset shows loss of H3K27me3 [10, 14, 29]. None of these were present in this case. Among histopathological differentials, neurofibroma was unlikely because it is typically unencapsulated, interdigitates with the parent nerve, and shows patchier/weaker S-100 with intralesional axons, whereas our lesion had a complete capsule, Antoni A/B architecture with Verocay bodies, and diffuse strong S-100. Neurofilament immunostaining demonstrates intralesional axons in neurofibroma, whereas in schwannoma the axons are displaced to a compressed peripheral rim. Consistent with Table 2, diffuse S-100/SOX10 positivity and lack of epithelial/gynecologic markers distinguish schwannoma from metastatic nodes; perineurioma was also unlikely (epithelial membrane antigen [EMA]/glucose transporter 1 [GLUT-1]/claudin-1 profile) [31]. Cellular or “ancient” schwannoma can mimic malignancy, but retention of a thick capsule, perivascular hyalinization, lack of coagulative necrosis and high mitotic activity, and diffuse S-100 favor a benign diagnosis over low-grade MPNST [10, 20, 22]. Non–nerve-sheath mimics were considered and dismissed based on morphology and immunoprofile: leiomyoma/leiomyosarcoma (α-smooth muscle actin [α-SMA]/desmin/h-caldesmon positivity and S-100 negativity) [32], solitary fibrous tumor (signal transducer and activator of transcription 6 [STAT6] nuclear/cluster of differentiation 34 [CD34] positivity with staghorn vasculature and S-100 negativity) [33], paraganglioma (zellballen architecture with chromogranin/synaptophysin positivity and S-100 limited to sustentacular cells) [34], and metastatic carcinoma from the coexisting ovarian primary (cytokeratin/PAX8/WT1 positivity) [35]. After complete excision, recurrence of benign retroperitoneal or pelvic schwannoma appears uncommon in contemporary series; higher rates reported historically likely reflect incomplete resections and heterogeneous “neurogenic tumor” groupings [18, 19, 36]. Functional outcomes are generally excellent when the epineurial plane is maintained, and pelvic or presacral series document early mobilization and durable pain relief after minimally invasive resection [3, 28, 37-40]. Our patient remains disease-free 32 months after surgery with preserved adduction and no neuropathic pain, consistent with these data.

include the single-patient design, absence of preoperative MRI neurography, an immunohistochemical panel limited to S-100 for the resected ONS, and lack of intraoperative neuromonitoring. Even so, the convergence of imaging review, intraoperative findings, classic histology, and favorable functional and oncologic outcomes supports the conclusion that meticulous nerve-sparing is feasible when ONS coexists with advanced ovarian cancer. In summary, during ovarian cancer cytoreduction a stable, well-circumscribed pelvic sidewall lesion interpreted as a “node” warrants scrutiny for neurogenic origin. Recognizing nerve continuity on MRI and applying epineurial plane dissection can preserve adductor function without compromising oncologic objectives, while avoiding unnecessary nerve sacrifice. 6 Conclusion In ovarian cancer cytoreduction, a stable, well-circumscribed pelvic sidewall mass should be assessed for a neurogenic origin. When CT localizes the lesion along the obturator canal and the mass remains unchanged after chemotherapy, a structured risk–benefit review can support deferring biopsy if open surgery is planned or percutaneous access is unsafe and proceeding with nerve-sparing enucleation; pathology then confirms schwannoma, with surgery serving as definitive treatment. Close coordination among radiology, gynecologic oncology, and nerve pathology/surgery helps preserve function without compromising oncologic goals. Author Contributions Ning Su: conceptualization, investigation, supervision, writing – original draft, writing – review and editing. Li Wang: data curation, methodology, visualization, writing – review and editing. Acknowledgments We thank Dr. Jianbo Zhang (Department of Pathology, Henan Cancer Hospital) for his guidance and assistance in drafting the section on the differential diagnosis of ONS. Ethics Statement Per institutional policy, single-patient case reports do not require formal IRB/ethics approval. The work adhered to the Declaration of Helsinki. Consent Written informed consent was obtained from the patient to publish this report in accordance with the journal's patient consent policy. Conflicts of Interest The authors declare no conflicts of interest. Data Availability Statement The data supporting the findings of this study are available from the corresponding author upon reasonable request.