Fine structure of a cerebellar "fibroma"

The fine structure of an intracerebellar "fibroma" has been examined. The tumor consists of irregularly-shaped cells connected by well developed junctional complexes. Unusual, fenestrated capillaries with extremely narrow and irregular lumens are frequent. Collagen fibers are not common but the wide extracellular spaces contain large amounts of dense, granular or fibrillar material. The dense material coats the tumor cells and is a apparently secreted from small vesicles found within these cells.