Desmoplastic Small Round Blue Cell Tumor in a Young Adult Man: A Rare Case of Abdominal Sarcoma.

BACKGROUND Desmoplastic small round cell tumor (DSRCT) is a rare and highly aggressive soft tissue sarcoma, mainly occurring in male adolescents and young adults. It most commonly arises from the peritoneum and is characterized by the EWSR1-WT1 fusion gene. Patients typically present with widespread intra-abdominal disease and have a poor prognosis, with a 5-year survival rate of less than 15%. CASE REPORT A 23-year-old man presented with acute right upper quadrant abdominal pain, significant unintentional weight loss, early satiety, and constipation. Computed tomography (CT) of the abdomen and pelvis revealed multiple large hepatic masses, mesenteric lymphadenopathy, and duodenal thickening with partial luminal narrowing. CT-guided biopsy of a hepatic mass was performed but was inconclusive. Subsequent upper endoscopy with duodenal biopsy revealed a characteristic perinuclear dot-like Desmin staining pattern consistent with small round blue cell tumor, with immunohistochemistry positive for epithelial and myogenic markers. The patient was referred to a sarcoma center where he was started on systemic chemotherapy with a VAC/IE (vincristine, doxorubicin, cyclophosphamide/ifosfamide, etoposide) regimen. CONCLUSIONS This case highlights the diagnostic complexity of DSRCT, particularly in atypical liver-dominant presentations, and reinforces the importance of comprehensive tissue sampling and molecular confirmation to guide early, appropriate therapy. Continued research into targeted strategies is crucial to improve outcomes in this aggressive malignancy.