(SUB-eh-PEN-dih-mul JY-unt sel AS-troh-sy-TOH-muh)

A benign (not cancer), slow-growing tumor that usually forms in the walls of fluid-filled spaces in the brain. The tumors are made up of large, star-shaped cells called astrocytes. Subependymal giant cell astrocytomas are common in patients with tuberous sclerosis (an inherited disorder in which benign tumors form in the brain and other parts of the body). Also called SEGA.