Giant retroperitoneal mass in a young male.

Retroperitoneal fibromatosis, also referred to as retroperitoneal desmoid-type fibromatosis, is an extremely rare, benign but locally aggressive mesenchymal neoplasm originating from the musculoaponeurotic system. Owing to their indolent growth and nonspecific presentation, these tumors are often asymptomatic at an early stage. When symptoms do occur, they usually result from mass effect on the adjacent structures. We report a 19-year-old male who presented with progressive abdominal distension for 2 years along with a massive abdominal lump occupying all quadrants of the abdomen. Imaging revealed a huge retroperitoneal mass with internal calcification and necrotic components. Core biopsy was consistent with fibromatosis. The patient underwent successful surgical excision of a 12 kg tumor. Postoperative recovery was uneventful, and follow-up at 6 months revealed no recurrence. Since the incidence is rare, maintaining a high index of clinical suspicion along with the use of imaging techniques, such as ultrasonography and CT/MRI scans, is essential for diagnosis. However, histopathology followed by immunohistochemistry is regarded as the gold standard for definitive diagnosis. The primary treatment approach is complete surgical removal with negative margins. Adjuvant therapies may be contemplated in instances of recurrence or when the tumor is unresectable. Early recognition and multidisciplinary management are crucial to optimize outcomes in patients with retroperitoneal fibromatosis. Due to the high recurrence rate, long term follow-up is essential.