However, since both tumors are rare, we agree with Vang and Kempson [40] that HMB-45 immunostaining should be performed on all epithelioid uterine tumors, not only to better delineate the features of both epithelioid smooth muscle tumors and PEComas, but due to the possibility of an association between the latter and the tuberous sclerosis complex (TSC). The gene discussed is PMEL; the disease is neoplasm with perivascular epithelioid cell differentiation.