NF1 and neoplasm: It encodes neurofibromin, which inhibits the rat sarcoma virus/mitogen-activated protein kinase and phosphoinositide-3-kinase/mammalian target of rapamycin signaling pathways and thus reduces cell proliferation and differentiation, thereby inhibiting tumor growth.[2] Mutation of NF1 leads to a deficiency of neurofibromin, resulting in an excess of the active form of rat sarcoma virus–guanine triphosphatase, which promotes excessive growth of cells, resulting in nerve and skin damage[3] and various benign and malignant tumors.