Multiple granular-cell tumors of the ascending colon: microscopic study.

Light and electron microscopic study of a case of multiple granular-cell tumor of the ascending colon is presented, and the relevant medical literature is reviewed. It seems that the biologic behavior of this tumor in the colon does not differ from that in other locations. Histologically, a few granular cells are seen in neural tissue in the vicinity of the tumor, suggesting a close relation of the tumor to the neural tissue. Electron-microscopically, the granular cells resemble Schwann cells more closely than neural cells and axons. Histochemically, the granules of the tumor cells show autofluorescence and high activity of acid phosphatase, which was located electron-microscopically in the limiting membranes and matrices of the granules. It is suggested that the granular-cell tumor is a neoplasm of Schwann-cell origin with a unique metabolism that causes acceleration of autophagocytosis and accumulation of ceroidlipofuscin.