Epithelioid sarcoma in children and adolescents. An immunohistochemical study.

Six cases of epithelioid sarcoma were studied by conventional light microscopy and immunohistochemistry. The six cases account for 1.4% of the 417 cases of soft tissue sarcoma collected at the Paediatric Tumor Registry, Kiel. The average age of the five male and one female patient was 10.8 years (median: 13 years). Particular clinical findings included the location of the tumours; three were found in the pelvis, two in the head and neck, and one in the hand. Four patients are living without disease, and one patient died of disease three years after diagnosis. Histologically, four of the six tumours revealed multinucleated giant cells. Immunohistochemically using a panel of mono- and polyclonal antibodies all cases stained positively for vimentin, cytokeratin, epithelial membrane antigen (EMA), and human milk fat globulin (HMFG-2). Five cases were positive for neuron specific enolase (NSE), and three stained positively for protein S-100. A positive reaction for alpha-1-antichymotrypsin was noted in two cases. These immunohistochemical findings attest to the multidirectional differentiating capabilities of epithelioid sarcoma and support the concept of derivation from a multipotent mesenchymal stem cell.