Adult-onset primary retroperitoneal cystic lymphangioma displacing the inferior vena cava: laparoscopic management of a triple-rarity case from Nepal and review of recent literature.

Introduction and importance: Lymphangiomas are rare benign lymphatic malformations, predominantly affecting children in the head and neck region. Retroperitoneal cystic lymphangioma (RCL) accounts for fewer than 1% of all lymphangiomas. Adult-onset primary RCL is exceptionally rare, with fewer than 200 cases documented in the global literature. We report what appears to be the first such case from Nepal, based on a review of available published literature. Case presentation: A 40-year-old woman presented with right back pain, a lumbar mass, and early satiety. Tumor markers were unremarkable. Initial ultrasonography misidentified the lesion as a probable ovarian cyst. Contrast-enhanced computed tomography (CECT) revealed a septated retroperitoneal cyst of size 7.0 × 5.9 × 5.7 cm causing significant medial displacement of the inferior vena cava (IVC). Laparoscopic exploration confirmed the retroperitoneal origin. Following controlled aspiration of serous fluid, laparoscopic marsupialization was performed with meticulous IVC and ureteric preservation. Histopathology confirmed cystic lymphangioma. The patient was discharged on postoperative day 4 without complications. Clinical discussion: RCL frequently mimics ovarian or mesenteric pathology on ultrasonography, making CECT essential for operative planning. When complete excision poses prohibitive hemorrhagic risk due to IVC proximity, laparoscopic marsupialization represents a justified and safe alternative. A recurrence risk of 10-13.6% following conservative surgical management mandates structured long-term annual surveillance. Immunohistochemistry (D2-40, CD31, and CD34) is recommended for definitive diagnosis where laboratory resources permit. Conclusions: This case involving a rare tumor type, an exceptionally rare anatomical location, and an atypical adult age of onset demonstrates that laparoscopic management of RCL with major vascular displacement is feasible in resource-limited settings. At 6-month follow-up, no recurrence was detected and the IVC had returned to its anatomical position. This represents a provisional early outcome; long-term surveillance remains mandatory given the established late recurrence risk.