As is well-known, the development of PEComas is closely associated with dysregulated mTORC1 activity, which is often due to a functional loss of TSC1 or TSC2. Although the function of folliculin is not fully understood, folliculin and mTORC1 are considered to be functionally related in the cellular signaling pathway; i.e., folliculin acts as a GTPase-activating-protein for RagC/D for the recruitment of mTORC1 to lysosomes, where mTORC1 exerts its function [11, 24]. The gene discussed is TSC2; the disease is neoplasm with perivascular epithelioid cell differentiation.