TSC1 and neoplasm with perivascular epithelioid cell differentiation: For a series of 15 PEComas, Kenerson et al. [14] reported the immunohistochemical evidence of mTORC1 activity, which suggests loss of TSC1 or TSC2. The loss of heterozygosity in the TSC1 or TSC2 region has also been reported in seven cases of PEComa by Pan et al. [15].