Desmoplastic Small Round Cell Tumor of the Abdomen: A Case Report

Background Desmoplastic small round cell tumor (DSRCT) is a rare and highly aggressive mesenchymal neoplasm that predominantly arises from the serosal surfaces of the peritoneum, most commonly affecting young males. Due to its rarity, overlapping histologic features with other small round blue cell tumors, and dependence on specialized immunohistochemical and molecular studies, diagnosis can be challenging. Case Presentation A 23‐year‐old Bahraini male presented with a 9‐month history of abdominal pain, fullness, and distention. Physical examination revealed a large, palpable intra‐abdominal mass, estimated to be 30 × 20 cm in size. Imaging studies, including abdominal ultrasound and computed tomography scan (CT scan), demonstrated a single, large intra‐abdominal mass centered within the right middle abdominal mesentery. The patient subsequently underwent an exploratory laparotomy, during which the identified abdominal mass was surgically resected. Histopathological analysis suggested the diagnosis of desmoplastic small round cell tumor, although the C‐terminus WT1 antibody was unavailable and only the N‐terminus WT1 was used; the diagnosis was established through combined morphologic assessment, immunohistochemistry, and confirmation of EWSR1 gene rearrangement by fluorescence in situ hybridization (FISH). DSRCT remains exceedingly rare in the Kingdom of Bahrain, and this case highlights the diagnostic challenges posed by its uncommon occurrence and reliance on careful immunohistochemical and molecular evaluation. Conclusion This case emphasizes the importance of maintaining a high index of suspicion for DSRCT in young males presenting with large intra‐abdominal. It highlights the critical role of integrating histopathology, immunohistochemistry, and molecular testing in achieving an accurate diagnosis, particularly in resource‐limited settings. Early recognition and multidisciplinary management remain essential in optimizing outcomes in this rare and aggressive tumor.