Intra-abdominal desmoplastic small cell tumor: a light microscopic, immunocytochemical, ultrastructural, and flow cytometric study.

The clinical, microscopic, and immunohistochemical features of 22 intra-abdominal desmoplastic small cell tumors are presented. Ten tumors also were studied by electron microscopy, and flow cytometry was performed in 11 cases. Nineteen patients were male and three were female; their ages ranged from 17 to 38 years (mean, 27 years). With the exception of one case, which arose in the scrotum, all the tumors originated within the abdomen or pelvis and multiple peritoneal nodules were typical. Five tumors also involved the retroperitoneum. The study demonstrates that the range of histology these tumors can display is broader than has been realized previously. The immunohistochemical and ultrastructural findings show evidence for epithelial, mesenchymal, and neuroendocrine phenotypes, raising the possibility that the tumors may be blastomas. Nine tumors were diploid, one tetraploid, and one aneuploid. Sixteen patients died of widespread metastases 8 to 50 months (mean, 25 months) from the time of diagnosis, and five were alive with known evidence of disease. One patient had no evidence of recurrence, but the follow-up of the case was only 10 months.