A case of intra-abdominal desmoplastic small round cell tumor

Background:Desmoplastic small round cell tumor (DSRCT) is a recently recognized tumor that mainly affects the serosal surfaces of young males. It consists of nests of small round tumor cells and fibrous connective tissue surrounding the tumor cell nests. Since the tumor cells of DSRCT express various differentiation markers, the histogenesis of DSRCT is a matter of controversy. Case:A 31-year-old man was admitted for abdominal discomfort and a tumor of the ileocecal region. Computer tomography depicted the ileocecal tumor and revealed metastatic foci in the liver. The ileocecal tumor was resected after chemotherapy, and an imprint cytology specimen showed a number of tumor cell nests. The tumor cells were small rounded cells with scant cytoplasm and granular nuclear chromatin. These histological findings were compatible with typical DSRCT. Immunohistochemically, the tumor cells were positive for cytokeratin, epithelial membrane antigen, vimentin, desmin, S-100, and neuron-specific enolase. Electron-microscopic examination revealed paranuclear aggregation of intemerdiate filaments, and a few desmosomes. Conclusion: DSRCT tumor cells are difficult to differentiate from the cells of other small round cell tumors in cytological specimens, but the clinical findings and nested pattern seen on low-power examinations of imprint specimens are suggestive of DSRCT. An awareness of DSRCT during cytological examinations is also important in making the diagnosis.