Postmenopausal intra-abdominal desmoplastic small cell tumor

Intra-abdomlnal desmoplastic small cell tumor (DSCT) usually occurs In infants and young male adults. A case of DSCT occurring in a 60 year old female Is described. No other apparent primary origin was detected. A mesocolon tumor, measuring 23times12times10cm, was composed predominantly of round to spindle cells which showed epithelioid- and focally sarcomatous arrangements. Irnmunohlstochemically, the tumor cells showed perinuclear dot-like staining of CAM5.2, many cells expressed HHF35, and some cells contained vimentin, epithelial membrane antigen, desmln, alpha-smooth muscle actin, neuron-specific enolase, or Leu 7. Electron microscopic examination showed that the tumor cells had mesenchymal-fibroblastic features. The tumor had an aneuploid DNA content with high S-phase fraction. The patient, who was treated with adjuvant chemotherapy, was alive, having had three recurrences in 36 months. In the second and third recurrent lesions, increased cellular atypla and fascicular arrangements of spindle cells were observed. DSCT should be included in differential diagnoses of postmenopausal pelvic tumors which show light-microscopically and immunohistochemically divergent phenotypes.