Desmoplastic Small Round Cell Tumor Presenting as Bloody Ascites: A Case Report and Literature Review

Background: Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive malignancy that predominantly affects young male patients. Its nonspecific clinical presentation and low diagnostic yield from ascitic fluid cytology pose a significant diagnostic challenge, particularly when presenting as ascites of unknown origin. Case Presentation: A 30-year-old previously healthy young man presented with a 4-week history of progressive abdominal distention, intermittent fullness, unexplained weight gain, and bloody ascites. Cytology from paracentesis and tumor markers were nondiagnostic. Imaging revealed omental caking and multiple peritoneal nodules, suggestive of peritoneal carcinomatosis. Diagnostic laparoscopy identified extensive tumor seeding, and biopsy confirmed DSRCT based on histopathology, immunohistochemistry, and the presence of an EWS-WT1 fusion transcript on cytogenetic analysis, establishing the diagnosis of DSRCT. Chemotherapy was recommended; however, the patient’s condition deteriorated rapidly, and he died within a few weeks before receiving treatment. Conclusions: DSRCT, although rare, is noted for aggressiveness and rapid progression and therefore should ideally be considered in the differential diagnosis of bloody ascites in young male patients, even when initial cytology is negative. Early application of diagnostic laparoscopy and biopsy may facilitate timely tissue diagnosis, particularly when imaging mimics peritoneal carcinomatosis.