Granular cell astrocytoma.

Granular cell astrocytoma (GCA) is a rare type of malignant brain tumor with distinct morphologic features and aggressive clinical behavior. Almost all GCAs occur in the cerebral hemispheres. It is characterized by a prominent component of bland-looking granular cells. The tumor cells are usually positive for glial fibrillary acidic protein, S100, CD68, and epithelial membrane antigen. The most important differential diagnoses include a number of reactive lesions such as cerebral infarction, multiple sclerosis, and progressive multifocal leukoencephalopathy. Electron microscopic study reveals that the granules of GCA correspond to an increased number of intracytoplasmic lysosomes. The histogenesis of GCA is still unclear, but most people believe it originates from astrocytes. Loss of 9p and 10q were identified in almost all cases of GCA, but they are not specific for this tumor. Surgical excision plus postoperative chemotherapy or radiotherapy is the choice for most patients with GCA.