Intra-abdominal desmoplastic small round cell tumor.

BACKGROUND: Intra-abdominal desmoplastic small round cell tumor is a rare malignancy with a predilection for young males. Unique histological and immunocytochemical features distinguish the tumor from other members of the family of small round cell tumors of infancy and childhood. The aggressive nature of tumor spread, relative insensitivity to chemotherapy, and generally incomplete resectability result in a very poor prognosis. The authors report a case of a 39-year-old man with diffuse abdominal and pelvic involvement of intra-abdominal desmoplastic small round cell tumor treated with aggressive chemotherapy and surgery. METHODS: Computed tomography (CT)-guided biopsy of an omental mass was performed. Histologically, discrete nests of uniform closely packed malignant cells were distributed in a background of focally desmoplastic stroma. Immunocytochemistry demonstrated positivity for epithelial, mesenchymal, and neural markers. On the basis of these unique histological and immunohistochemical characteristics, the diagnosis of desmoplastic small round cell tumor was made. The patient was treated with aggressive neoadjuvant chemotherapy consisting of a high-dose alkylator -based combination regimen, followed by surgery. RESULTS: The patient had a 10 to 15 percent regression in tumor mass in response to chemotherapy. Laparotomy revealed two large omental masses, another large mass adherent to the left colon and pelvic sidewall, and diaphragmatic, peritoneal and mesenteric studding with small nodules. Complete surgical resection was not possible. CONCLUSIONS: Intra-abdominal desmoplastic small round cell tumor remains an aggressive malignancy with an extremely poor prognosis. Although some response to chemotherapy may be possible, complete resection is rare, and surgical efforts are generally palliative.