Subependymal Giant Cell Astrocytoma
Higher magnification showing several cells with neuron like nuclei and astrocyte-like cytoplasm. SEGA is a benign tumor (WHO Grade I) and may be hamartomatous rather than a true neoplasm. They do not undergo malignant transformation and are easily resectable. However, they have prognostic implications due to their association with tuberous sclerosis. MOLECULAR GENETICS: There are two loci involved in tuberous sclerosis. TSC1 on chromosome 9q34 encodes hamartin; a second locus TSC2 on 16p13.3 encodes tuberin. The two proteins form a complex that inhibits the kinase mTOR which is a regulator of protein synthesis, anabolic metabolism, as well as cell size. Consequently, hamartomatous lesions seen in tuberous sclerosis such as subependymal giant cell astrocytoma and cardiac rhabdomyomas have voluminous cytoplasm.