Gemistocyte

A gemistocyte (sg. /dʒɛˈmɪstəsaɪt/ je-MIS-tə-syt) is a swollen, reactive astrocyte. These cells usually appear during acute injury; after that, they gradually shrink in size.

Astrocytes participating in gliosis are referred to as reactive astrocytes. They have a large cytoplasmic mass, long, branching processes, and increased cytoplasmic filaments. Such astrocytes are also known as gemistocytic astrocytes from a Greek word that means to fill up. Gemistocytes are also found in some chronic diseases and within certain brain tumors, which suggests the presence of a long-lasting pathological reaction. In the context of cancer (gemistocytic astrocytomas), gemistocytes are known to dedifferentiate to a high grade (III or IV) glioma (i.e. glioblastoma multiforme) at a rapid pace, usually indicative of a poor prognosis.