Identification of desmosomes in the granular cell tumor. Implications in histologic diagnosis and histogenesis.

Electron-microscopic examination of a malignant granular cell tumor revealed cells with abundant granular and glycogen-containing cytoplasm and eccentric nuclei. Numerous junctional structures including desmosomes were identified between tumor cells which, moreover, displayed a pattern of gland formation with the presence of short microvilli in one pole of the cell. The presence of junctional structures may provide a feature for positive identification of this tumor by electron microscopy. The findings may also have implications to further our understanding of the histogenesis of this tumor. This case further raises the question of familiar occurrence of this tumor.