Epithelioid sarcoma or malignant rhabdoid tumor of soft tissue? Epithelioid immunophenotype and rhabdoid karyotype.

Two children and one young adult with extremity sarcomas demonstrating an aggressive clinical behavior are described. Histologically, all three tumors displayed features compatible with a deep-seated epithelioid sarcoma or with a malignant rhabdoid tumor of soft tissue. Immunohistologically, both vimentin and epithelial antigens were demonstrated; however, no desmin was detectable. In all three cases, the DNA profile was diploid. In one case, a trisomy of chromosome 2 was found in the tumor cells, a phenomenon also observed in embryonal rhabdomyosarcomas. It is concluded that, although the immunohistologic findings support the epithelioid character of the tumors, this chromosomal finding suggests a relationship with rhabdomyosarcomas and justifies the designation of rhabdoid.