Granular Cell Tumor (Myoblastoma) of RAT Brain
Granular cell myoblastoma is a rare tumor of which the nature and origin has been controversial. The cytogenesis of this tumor has been suggested as a neoplastic derivation from adult or embryonic muscle tissue, a histiocytic storage phenomenon, of neural origin and as a neoplasm derived from Schwann cells.This report presents the ultrastructure of a spontaneously occurring granular cell tumor from the brain of a 22 month old female Sprague- Dawley rat. Gross examination revealed an oval, gray external mass 3x4 mm in size and located on the cerebellar dorsal surface. This tumor was connected by a narrow stalk to a tumor mass located in the molecular layer of the cerebellum. The external tumor and the stalk were excised for electron microscopy (EM) and the remaining tumor mass, brain, and stalk were processed for light microscopy (LM).