A Case of Epithelioid Sarcoma

Abstract

A case of a 58-year-old man with epithelioid sarcoma is reported. Small nodular lesions, up to LOxl Gmrn in diameter, were present on the scalp, face and upper arm. On chest X-ray examination, the nodular lesions were noticed in the right upper and middle lung field.Biopsy specimen of a scalp nodule and lung lesion showed granulomatous changes composed of irregular-shaped eosinophilic cells with nuclear atypism, spindle-shaped fibroblast-like cells and a few multinucleated giant cells.Electron microscopic examination revealed that two types of cells, dark cells and light cells, were present in the dermal lesion. The cytoplasm of the dark cell contained a large amount of dilated rough-surfaced endoplasmic reticulum and well-developed protocollagen. This finding suggests that the dark cell tends to differentiate towards a fibroblast. Most of light cells had some underdeveloped rough-surfaced endoplasmic reticulum but no filamentous elements. A few exceptional light cells have considerable rough-surfaced endoplasmic reticulum. It therefore seems that the clear cell has a potencial for differentiation towards a histiocyte.These findings suggest that epithelioid sarcoma cells derive from undifferentiated mesenchymal cells.