Intraabdominal Desmoplastic Small Cell Tumors with Divergent Differentiation: Report of two cases with immunohistochemical and ultrastructural studies

ABSTRACT

We studied two intraabdominal desmoplastic small cell tumors. The patients were two men, 37 and 23 years old, with jaundice and palpable abdominal masses. On exploratory laparotomy, each patient revealed a huge mass in the greater omentum with disseminated peritoneal seeding, measuring 32 cm and 11 cm in its greatest dimension, respectively. The tumor involved the diaphragm, rectal shelf, and cul de sac in case 1, and it involved the porta hepatis, retroperitoneum, and serosal surface of the ascending and transverse colon in case 2. Omentectomy of the huge mass and satellite masses was performed in each patient. Both tumors showed nearly the same histopathologic features. The histologic pattern was suggestive of a metastatic small cell carcinoma, but there was no specific, single primary site. The tumors consisted of variably sized, discrete islands of epithelial-like small cells in dense desmoplastic stroma. The tumor cells revealed divergent epithelial, mesenchymal, and neural differentiation by histologic, immunohistochemical, and electron microscopic observations. Only one cycle of chemotherapy including cisplatin and VP-16 was given in case 1 because of a subsequent hepatic problem, who, thereafter, showed massive intraabdominal recurrent tumors 6 months after diagnosis. In case 2, the poor condition of the patient had made chemotherapy and radiotherapy impossible. Case 2 died of disseminated intravascular coagulation following progressive cachexia 7 months after diagnosis.