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. They are usually present in anoxic-ischemic brains, which occurs when there is a complete lack of blood flow to the brain. The human brain contains many cells that can impact gliosis, including endothelial progenitors, fibroblast lineage cells, different types of inflammatory cells, and various types of glia and neural-lineage progenitor cells, which include astrocytes. Gliosis occurs when the body creates more, or larger, glial cells that cause scars in the brain that impact body functions. The human body has many body functions to maintain homeostasis because gliosis can occur immediately upon injury. Anoxic-ischemic brains usually occur in patients who have had cardiac arrest and prolonged attempt at cardiopulmonary resuscitation. Functions in the body When present in anoxic-ischemic brains, gemistocytes are regularly encountered in glial neoplasms, also known as glioma, which is a type of tumor that occurs in the brain and spinal cord. Usually, gliomas begin in the glial cells that surround the nerve cells to help them function. Many gliomas exhibit cells that do not exist in normal brain tissue and are not seen in glial differentiation. Of these gliomas are astrocytomas, which is a type of cancer that occurs in the brain or spinal cord. The main role of astrocytes is to maintain brain homeostasis and neuronal metabolism. When the astrocytes become activated, they begin to respond to damage. Astrocyte activation, known as astrogliosis, responds to neurological trauma, infections, degradations, epilepsy, and tumorigenesis. Each neurological insult plays a major role in astrocyte activation and response to that specific damage. In some astrocytomas, the number of gemistocytes is extremely overwhelming, terming it a “gemistocytic astrocytoma.” Not only are gemistocytic cells present in astrocytomas, but they are also found in various glial tumor cells; for example, oligodendrogliomas, mixed oligoastrocytomas, glioblastomas, and pleomorphic xanthoastrocytomas. Gemistocytes are known to have a large cytoplasmic mass, long, branching processes, and increased cytoplasmic filaments. The cytoplasm of gemistocytes stains positive for glial fibrillary acidic protein, GFAP. While the intermediate filaments in gemistocytes are diffused throughout the cytoplasm, which indicates cellular disintegration. Within these different tumor types, the term “mini-germistocytes” is used for smaller gemistocytes, that are usually found in oligodendroglial