Laparoscopic Resection of a Rare Retroperitoneal Dermoid Cyst in a 78-Year-Old Woman: A Case Report.

All research procedures involving human subjects were conducted in compliance with the ethical guidelines established by the relevant institutional and/or national research committees, as well as the principles outlined in the Declaration of Helsinki (as revised in 2013). Prior to the study’s publication and the release of any associated imagery, written informed consent was secured from the patient. A 78-year-old woman was admitted in July 2024 due to an increased left renal occupancy detected during a recent health examination. She had experienced left lower-abdominal pain without obvious cause 9 years before. She came to our outpatient clinic and underwent a CT scan, which revealed a left renal occupancy. She refused surgical treatment at that time. Recently, she visited our hospital again due to the discovery of a left renal occupancy on a physical examination ultrasound at another hospital. An outpatient CT showed a retroperitoneal occupancy. Urine sediment with bacteria 153.00/ul; serum cytokeratin CYFRA 211 is 3.93 ng/mL; biochemical tests revealed creatinine 89 umol/L. Enhanced CT in September 2015 ( Figure 1 ) showed a cystic mass in the retroperitoneal area at the left renal hilum (4.8×3.7 cm), with the renal vein being displaced anteriorly, showing mild peripheral enhancement (CT value of 10–30 HU). The July 2024 renal artery computed tomography angiography (CTA) ( Figure 2 ) revealed a 5.2×4.0 cm cystic mass with increased density, calcification at the edges, and minimal enhancement, which displaced the left ureter and compressed the renal pelvis, resulting in hydronephrosis and renal cortex thinning, and the retroperitoneal cystic mass at the left renal hilum was diagnosed as a neurogenic tumor with cystic degeneration on CTA. Renal dynamic imaging and glomerular filtration rate (GFR) measurement in July 2024 showed that right kidney had a GFR of 58.2 ml/min, while the left kidney had severe renal impairment, with a GFR of 10.4 mL/min, indicating significant functional loss of the left kidney. The patient was diagnosed with a retroperitoneal cystic mass causing severe functional impairment of the left kidney, while the right kidney maintained normal function. We therefore decided to proceed with laparoscopic radical resection of the mass, left nephrectomy, and retroperitoneal lymphadenectomy. Postoperatively, the patient had lymphatic drainage with lymphorrhea from the renal fossa due to lymph node dissection. Lymphatic drainage gradually decreased over the course of a week. After 3 consecutive days of drainage being less than 50 mL, the drainage tube was successfully removed. At 6-month follow-up, she had an uneventful recovery and remained asymptomatic. She consented to undergo further surveillance. After extensive counseling and discussion regarding the examination and medical history, she underwent laparoscopic resection of the left retroperitoneal mass, left nephrectomy, and retroperitoneal lymphadenectomy. 1) A urinary catheter was placed preoperatively. 2) The patient was positioned in the right lateral decubitus position to facilitate locating structures. 1) Intraoperative monitoring: Intraoperative blood pressure, oxygen saturation, and respiration were continuously monitored. 2) Dissection: Dissection was carried out along the psoas major muscle medially to expose the renal artery and vein. These vessels were clamped, cut with scissors, and isolated. 3) Kidney Removal: The kidney was carefully peeled from the surrounding fat capsule, with no ectopic vessels or bleeding encountered on the surface. 4) Ureter Separation: The dilated ureter was identified, separated downward toward the iliac vessels, clamped, and cut with scissors. 5) Final Steps: The left kidney and retroperitoneal mass were removed. A drainage tube was placed in the retroperitoneal area. The surgery was uneventful, with no intraoperative complications. Gross examination: Figure 3 shows a cyst measuring 7×5×3 cm at the perinephric peritoneum near the upper pole of the kidney, with walls 0.1–0.2 cm thick, containing grayish-white and grayish-yellow tissue that resembles bean curd residue. Figure 4 shows a 3×1.5×0.2 cm gray-brown tissue with scattered yellow granular material on the surface, 3.5 cm from the cyst, with an adjacent 3×2×1.2 cm cyst with a 0.2–0.3 cm wall thickness. Microscopic examination: Hematoxylin and eosin (H&E) staining confirmed the diagnosis of dermoid cyst. Figure 5 shows a cyst lined by keratinizing squamous epithelium with disorganized skin appendages and fibrous tissue in the adjacent cyst wall. Figure 6 shows a cyst lined by keratinizing squamous epithelium with adjacent connective tissue, mature adipose tissue, blood vessels, and some smooth muscle.

Retroperitoneal tumor (RPT) is an extremely rare tumor occurring in the retroperitoneal region, with malignant mesenchymal tumors being the most common, and benign tumors being less common, especially dermoid ones [ 1 – 3 ]. Dermoid cysts are a pathological variant of mature teratoma [ 4 , 5 ]. Mature teratomas are tissues composed of fully differentiated cells originating from all 3 germ layers (ectoderm, mesoderm, and endoderm) [ 6 ]. They are most common in females and children [ 7 , 8 ] and exhibit a left-sided predominance [ 9 ]. In contrast, dermoid cysts derive principally from ectodermal elements [ 10 ]. Eighty-four percent of dermoid cysts occur in the head and neck region, while retroperitoneal dermoid cysts are exceptionally rare [ 8 ]. The wall of the dermoid cysts exhibit mature skin appendages, and their lumens are filled with keratin and hair [ 11 ]. This case report emphasizes the importance of early diagnosis and early treatment of such retroperitoneal benign tumors, and proposes optimized and standardized diagnostic and therapeutic protocols. These benign lesions in the retroperitoneum pose significant challenges due to their nonspecific clinical and imaging presentation, complex anatomical location, and potential for misdiagnosis as malignant tumors. In imaging examinations, although CT and MRI can distinguish between cystic and solid components [ 12 ], a definitive diagnosis of dermoid cysts is difficult based solely on imaging due to the lack of characteristic features. Due to the diagnostic ambiguity and the lack of standardized treatment protocols, surgeons have traditionally tended to assume that tumors in this region are malignant, opting for radical or even extended resections, which can lead to overtreatment [ 3 ]. We report the case of a 78-year-old woman who presented with hydronephrosis secondary to a solitary retroperitoneal mature cystic teratoma (dermoid cyst), which was successfully resected laparoscopically, and discuss the diagnosis, differential diagnosis, and treatment strategies for this disease. The article is presented in compliance with the CARE reporting checklist.

This case report underscores the diagnostic and therapeutic challenges associated with retroperitoneal cystic lesions, attributable to their exceptional rarity and the frequent absence of pathognomonic clinical manifestations [ 2 ]. These characteristics necessitate comprehensive preoperative imaging evaluation – an imperative for narrowing the differential diagnosis. Definitive determination of benign versus malignant pathology remains paramount for selecting appropriate surgical strategies [ 13 ]. Furthermore, even histologically benign retroperitoneal neoplasms can induce progressive compromise of adjacent organ function through mass effect, potentially culminating in irreversible sequelae, thereby necessitating timely surgical intervention. Retroperitoneal tumors (RPTs), occurring in the retroperitoneal space, are predominantly malignant mesenchymal tumors, such as liposarcoma and leiomyosarcoma [ 14 , 15 ]. In a Chinese study, 546 cases of RPT had a benign rate of 32.42% [ 16 ]; another study of 764 primary RPT patients showed that 308 were benign (40.31%), and only 19 cases were not of mesenchymal, neural, or lymphohematopoietic origin, of which 17 were benign [ 17 ]. Retroperitoneal cystic lesions (RCL), a subset of RPTs, include both non-neoplastic and neoplastic lesions, with congenital RCLs having an incidence rate of approximately 1/5750–1/250 000, and dermoid cysts are the rarest pathological type [ 2 , 18 , 19 ]. The term “dermoid cyst” designates a cyst of ectodermal origin, predominantly comprising a single tissue type – primarily skin and its adnexal structures [ 10 ]. In contrast, “mature cystic teratoma” denotes cysts containing a broader spectrum of tissues derived from all 3 germ layers. The size varies significantly, ranging from very small cystic masses to ones over 39 cm in diameter, with 80% of mature cystic teratoma measuring 10 cm or less in diameter [ 20 ]. Dermoid cysts are a subtype of mature cystic teratoma [ 4 , 5 ] and are histologically benign lesions [ 21 ]. Their cystic cavities are lined by squamous epithelium and primarily filled with sebaceous material. While most common in subcutaneous tissue, they can also develop beneath mucosal surfaces or within visceral organs. These cysts are most common in infants and mainly occur in the head and neck region, particularly the periocular area [ 22 , 23 ]. The dermoid cyst wall has mature skin appendages, and their lumens are filled with keratin and hair [ 11 ]. Additionally, dermoid cysts can be simply divided into congenital and acquired. Congenital cysts are caused by epithelial cells being encapsulated along embryonic closure lines, but can theoretically be present in any location along the pathways of ectodermal cell migration [ 24 ], while acquired cysts are caused by traumatic skin implantation into deeper tissue layers. Another classification method proposed by New and Erich divides them into 3 types: teratogenic congenital cysts, acquired cysts, and congenital inclusion cysts [ 25 , 26 ]. Furthermore, dermoid cysts arise from the entrapment of ectodermal elements along the lines of embryonic closure [ 11 ], which distinguishes them from mature teratomas, being more common in children and adolescents [ 27 ]. A search of PubMed for “retroperitoneal dermoid cyst” yielded 16 case reports published from 1969 to August 2024, with the most recent one reported in June 2024 [ 5 ], describing a case of uterine adenomyosis combined with a retroperitoneal dermoid cyst, which was successfully resected using the pararectal-transabdominal combined surgery approach. Patients may remain clinically silent, with retroperitoneal cystic masses discovered incidentally during imaging studies [ 13 ]. Alternatively, they can present with location-dependent symptoms such as renal colic [ 28 ], pelvic pain [ 29 ], or radicular pain [ 30 ]. This correlates with the current case where a perirenal dermoid cyst manifested as left lower quadrant discomfort. Furthermore, following cyst rupture, some patients have mild peritoneal irritation signs, such as tenderness or rebound tenderness, resulting from stimulation of adjacent tissues by cyst contents [ 31 ]. A search of the CNKI and Wanfang databases for “retroperitoneal dermoid cyst” from 1989 to 2024 yielded 6 case reports. In 1 case [ 32 ], due to the large size of the dermoid cyst, lymphatic vessel damage occurred during removal, leading to chylous ascites. Three other cases were closely related to adjacent organs. One case showed a close relationship with the liver and right kidney on CT, presenting as a right renal cyst, with moderate impairment of right kidney function, and only the mass was resected without nephrectomy [ 33 ]; another case of spontaneous rupture of retroperitoneal dermoid cyst through the vagina [ 34 ]; a third case was a dermoid cyst at the lower pole of the right kidney, where the renal function was not accurately assessed preoperatively, possibly due to limited technology at the time, and the cyst was large, leading to resection of the dermoid cyst combined with the right kidney [ 35 ]. These cases emphasize the importance of thorough preoperative evaluation and timely surgical intervention. Comprehensive preoperative assessment of tumor location, size, infiltration extent, and involved organ function is essential [ 36 ]. CT and MRI are the preferred methods for examining retroperitoneal cysts, which can observe the contents of dermoid cysts, distinguish between cystic and solid components, and are helpful for differential diagnosis [ 12 ]. Differential diagnoses include lipoleiomyoma, liposarcoma, lymphangioma, and bronchogenic cysts, all of which are benign except for liposarcoma, which is the most common and is more common in adults [ 27 ]. In dermoid cysts, there may be thin and uniform separation, rather than the linear, local, and irregular high-density shadows in liposarcoma. Nevertheless, CT and MRI scans still lack characteristic features for retroperitoneal dermoid cysts. Simultaneously, the symptoms and signs of patients rely on the size, location, and biological characteristics of retroperitoneal tumors, which are not specific [ 37 ]. Therefore, pathological examination is currently the only definitive diagnostic method. According to the consensus of Chinese retroperitoneal tumor experts [ 3 ], image-guided core-needle puncture biopsy is recommended if the tumor is difficult to resect using imaging assessment, or if differential diagnosis is required. For patients with difficult diagnosis, multiple and repeated puncture biopsies can be performed. Notably, percutaneous biopsy may yield inconclusive results, revealing only benign adipose tissue [ 30 ]. Additionally, intraoperative frozen section pathology can aid in the optimization and adjustment of the surgical plan. The diagnosis still depends on pathological biopsy, but the pathological diagnosis of dermoid cysts is mainly based on histological features, not specific immune markers [ 38 ]. The main treatment for RPT is surgery, and the main treatment for dermoid cysts is total cystectomy [ 39 ], avoiding open abdominal surgery, with laparoscopic surgery being the first choice. For deep or large cysts, a combined laparoscopic and perineal approach may be considered [ 40 ]. Surgical resection of the surrounding tissue of the cyst can prevent residual cyst walls, thereby avoiding severe chronic conditions that can lead to malignancy [ 41 ], and care should be taken when the tumor is close to large vessels in the retroperitoneal area. Intraoperatively, ultrasound-guided resection – particularly effective in differentiating lesions with cystic components from solid tissues – significantly contributes to complication prevention [ 42 , 43 ]. Resection of retroperitoneal masses poses significant surgical challenges due to their proximity to critical structures such as the intestines and ureters, increasing surgical difficulty and risk of injury to adjacent organs. Surgery can cause various complications, including vascular system, gastrointestinal system, and hepatobiliary pancreatic system complications, as well as urinary system complications such as acute renal failure and ureteral fistula after combined nephrectomy, and skeletal motor system complications such as lower-limb sensory or motor disorders [ 3 ]. The main surgical approach is multi-organ and major vascular resections, with the most common being kidney, colon, adrenal gland, and small intestine combined resection [ 44 ].

The key features of this case included a large retroperitoneal mass compressing the upper urinary tract, resulting in hydronephrosis and severe renal impairment, and presented as a rare solitary retroperitoneal mature cystic teratoma (dermoid cyst). This case highlights the diagnostic and therapeutic challenges of retroperitoneal cystic lesions, which are exceedingly rare and typically lack specific symptoms and signs. These characteristics necessitate a thorough physical examination, combined with comprehensive preoperative imaging, which is essential to narrow the differential diagnoses. Determination of the benign or malignant nature of retroperitoneal tumors is crucial for selecting the appropriate surgical approach, which may involve image-guided core-needle biopsy and intraoperative frozen section pathology to guide the extent of resection, with consideration of combined organ resection if necessary. Concurrently, intraoperative ultrasonography facilitates identification of cystic lesions – a critical capability for mitigating procedure-related complications. Early surgical intervention is also crucial for benign retroperitoneal tumors, as their increasing size can compress surrounding organs, impair their function, and potentially lead to irreversible damage. In our case, the massive cyst compressing the left renal pelvis and ureter led to nearly complete loss of left kidney function, and the retroperitoneal region’s highly complex anatomical structure necessitates that surgeons possess superior laparoscopic skills. In summary, the findings of this case emphasize the importance of comprehensive evaluation, including imaging and preoperative as well as intraoperative pathology, followed by selecting the appropriate surgical scope and timely surgical intervention to treat a retroperitoneal cyst. There were several limitations in the present case report. Firstly, the literature on the type of disease reported in this article is relatively scant, and there were no highly typical symptoms, signs, or radiological findings during the clinical diagnosis and treatment of this case. Therefore, further research on a broader sample is needed to aid in the diagnosis and treatment of this disease. Additionally, the pathological diagnosis of dermoid cysts primarily relies on morphological observation. The next step could involve exploring the specific antigens they express, providing a more solid basis for future diagnoses of such diseases. Despite these limitations, this case report provides references and experiences for the diagnosis and treatment of this disease and offers new insights into future research.