GRANULAR CELL TUMORS OF THE CENTRAL NERVOUS SYSTEM

Abstract

This paper describes two cases of granular cell tumor, the first such tumors believed to have arisen in the central nervous system with the exception of those in the neurohypophysis. The tumor in one case arose in the cervical spinal leptomeninges and in the other was located in a cerebral hemisphere. The light and electron microscopic characteristics were indistinguishable from granular cell tumors (myoblastomas) reported in other body sites. Ultrastructurally two cell types could be distinguished. The predominant form (Type II) was characterized by abundant cytoplasm filled with dense bodies, multivesicular bodies and vacuoles. A second smaller cell (Type I) contained few of the above organelles. It is considered likely that these cell types are evolutionary stages of a single kind of a cell in which Type I is transformed into Type II. Various cells, including Schwann cells, have been proposed as giving rise to granular cell tumors. The occurrence of these neoplasms in the central nervous system lessens the likelihood of a Schwannian source in all instances. An origin from Schwann cells of perivascular nerves cannot be excluded. The possibility remains that neoplasms designated as granular cell tumors may have more than one cell of origin.