Granular cell myoblastoma.

Electron microscopic observations in three cases of granular cell myoblastoma revealed that this tumor is made up of two types of cells. 1) Granular cells grouped into nests, surrounded by a basement membrane, and displaying characteristic inclusions. Numerous processes were observed close to these cells, showing filamentous and microtubular components lying parallel to their axes. 2) Satellite fibroblasts which included angulated bodies. The relationship between these two types of cells is discussed.