RHEB and neoplasm with perivascular epithelioid cell differentiation: PEComas are related to the genetic alterations of tuberous sclerosis complex (TSC), an autosomal dominant genetic disease associated with losses of TSC1 (9q34) or TSC2 (16p13.3) genes, which seem to have a role in the regulation of the Rheb/mTOR/p70S6K pathway.