TSC1 and pilocytic astrocytoma: This new classification defines as a separate group lower grade astrocytomas with a more circumscribed growth pattern, lack of IDH1/2 (isocitrate dehydrogenase 1 coding genes) alterations, and frequent mutations of BRAF (v-raf murine sarcoma viral oncogene homolog B1 coding for serine/threonine kinase) (i.e., in pilocytic astrocytoma, pleomorphic xanthoastrocytoma) or TSC1/TSC2 (tuberous sclerosis complex 1/2 encoding hamartin and tuberin) (in subependymal giant cell astrocytoma).