Desmoplastic small round cell tumor of the abdomen

A 21-year old woman presented with a 2-month history of abdominal pain. The diagnostic work-up disclosed a 17-cm intraperitoneal mass. Biopsy showed islets containing small round cells surrounded by abundant desmoplastic stroma. Immunohistochemistry was strongly positive for desmin and weakly positive for vimentin and neuron-specific enolase. Pathological diagnosis was intraabdominal round cell desmoplastic tumor. The patient underwent an intensive schedule of high-dose alkylator-based chemotherapy, the P6 protocol, designed by the Pediatrics Division of the Memorial Sloan-Kettering Cancer Center. She had a partial response and subsequently underwent resection of the residual mass followed by high-dose chemotherapy with stem cell support. Ten months later, the patient had disease progression and is currently receiving second-line chemotherapy.