Evidence supporting neural crest origin of an alveolar soft part sarcoma: an ultrastructural study.

A case of an alveolar soft part sarcoma was studied electron microscopically. This showed tumor cells separated by external lamina that incorporated desmosome-like structures. Well defined basal lamina separated several cells from underlying endothelial cells by a zone of tissue composed predominantly of fibrous long-spacing collagen. A unique finding was the presence within several tumor cells of well defined myelin sheaths and myelinated axons. Apart from various other intracellular organelles some of the cells contained closely aggregated fine filamentous structures: the so-called "angulate bodies." All these findings are interpreted as evidence for a tumor showing marked Schwann cell differentiation, and therefore, it is suggested that alveolar soft part sarcoma is histogenetically a neoplasm of the neural crest.