However, Cyclin D1 overexpression has been detected by immunohistochemistry in 5 cases of PEComas-NOS that were either malignant or had an uncertain malignant potential.12,21,39 The role of Cyclin D1 in the pathogenesis and progression of PEComas is becoming an area of interest. The gene discussed is CCND1; the disease is neoplasm with perivascular epithelioid cell differentiation.