INTRAABDOMINAL DESMOPLASTIC SMALL ROUND-CELL TUMOR OF THE PERITONEUM IN A YOUNG MAN

The desmoplastic small round cell tumor (DSRCT) has a predilection for involvement of the peritoneal surfaces of young adult men. The tumor has an extremely poor prognosis: despite aggressive therapy the patien ts usually die of disease within the first 2 years following diagnosis . The present report details the pathologic features of a pelvic tumor , which proved to be a DSRCT, arising in a previously healthy 24-year- old man. The light microscopic features were typical of a DSRCT-the tu mor cells were small and round, had inconspicuous cytoplasm, and were grouped into distinctive islands and cords that were dispersed in a fi brous stroma. The immunohistochemical features were likewise character istic of DSRCT in that the tumor cells were positive for cytokeratin, vimentin, epithelial membrane antigen, and desmin. Ultrastructurally, the tumor cells were distinguished by an abundance of intercellular ju nctions, cytoplasmic lipid droplets, cytoplasmic intermediate filament s, and an absence of surface microvilli. Recognition of this tumor typ e is important in view of both its clinical features (extremely poor p rognosis despite therapy) and its potential to shed some light on the nature of the family of lesions that has traditionally been classified by light microscopists as small round cell tumors.