A Case of Epithelioid Sarcoma Displaying Pluripotential Differentiation

A light and electron microscopic study was performed on surgical materials of an epithelioid sarcoma from a 47-year-old man who had diffuse induration in the left arm for 10 years. Surgery and immun ochemical therapy were of little help and he died in a course of one year with pulmonary metastases. Light microscopically, the tumor was composed of nodular proliferation of epithelioid cells in the main, but in some areas it showed pluripotential differentiation towards osteoblasts, rhabdomyoblasts, angioblasts, spindle cells and foamy cells. Electron microscopically, tumor cells in the epithelioid island contained in their cytoplasm abundant microfilaments showing tonofibril-like arrangement, which suggest that they are epithelial in origin, but they had neither desmosome nor basal lamina. Spindle cells showed ultrastructural features similar to those of fibroblasts, and foamy cells to those of fat cells. The biphasic pattern with epithelioid cells and spindle cells is consistent with the reported cases of epithelioid sarcoma, but pluripotential differentiation has not yet been described. The finding of the pluripotential differentiation indicates that the tumor has the features similar to malignant mesenchymoma.