Subependymal giant cell astrocytoma, light micrograph. Subependymal giant cell astrocytoma (SEGA) is a燽enign brain tumour (WHO Grade 1)爐hat is almost exclusively seen in the setting of爐uberous sclerosis. It affects 5% to 15% of patients with tuberous sclerosis and is usually diagnosed燽efore the age of 20 yrs. This爄ntraventricular tumour爄s usually located in the爈ateral or third ventricle爊ear the foramen of Monro and may cause爋bstructive hydrocephalus, although most cases are燼symptomatic. It composed of爀pithelioid, gemistocyte-like, and spindled cells. Several gemistocyte-like cells can be seen in this field.