A gemistocyte (/dʒɛˈmɪstəsaɪt/ jem-ISS-tə-syte; from Greek γέμιζω (gemizo) 'to fill up') is a swollen, reactive astrocyte.
Gemistocytes are glial cells that are characterized by billowing, eosinophilic cytoplasm and a peripherally positioned, flattened nucleus. Gemistocytes most often appear during acute injury; and eventually, shrink in size.[1] They are usually present in anoxic-ischemic brains, which occurs when there is a complete lack of blood flow to the brain. Anoxic-ischemic brains usually occur in patients who have had cardiac arrest and prolonged attempt at cardiopulmonary resuscitation.[2]