In a study aiming to distinguish PEComas from uterine smooth muscle tumors, twenty-one uterine PEComas and 45 SMTs were analyzed for PNL2; HMB45, Melan-A, Cathepsin-K, Desmin, and h-Caldesmon [19]. The gene discussed is CTSK; the disease is neoplasm with perivascular epithelioid cell differentiation.