Cutaneous PEComas Express CD10: Implications for the Classification of PEComas and the Differential Diagnosis With Metastatic Renal Cell Carcinoma

Cutaneous perivascular epithelioid cell tumors (PEComas) are peculiar, rare mesenchymal tumors of uncertain lineage. They show a characteristic epithelioid morphology, and they are usually composed of monomorphous clear-to-granular appearing perivascular cells. One of the main differential diagnoses with PEComas is a cutaneous metastasis from renal cell carcinoma (RCC). CD10 has been emphasized to be a crucial marker in the diagnosis of metastasis from RCC. Although visceral PEComas have been studied for CD10 expression, primary cutaneous PEComas have not. Although it could be assumed a priori that cutaneous PEComas would stain as their visceral counterpart, there is increasing evidence that cutaneous PEComas could actually be unrelated to PEComas from other organs. In this report, the author's studied three primary cutaneous PEComas, and included CD10 in our immunohistochemical studies. All three PEComas expressed the marker. They conclude that a CD10(+) clear-cell dermal tumor is not necessarily equivalent to a metastasis from RCC and that additional stains should be added to rule out PEComa, even if the biopsy or the panel of antibodies is limited.