Cytopathology of extra-renal perivascular epithelioid cell tumor (PEComa): a series of 7 cases and review of the literature

Introduction: Perivascular epithelioid cell tumor (PEComa) is a family of rare mesenchymal tumors consisting of histologically and immunohistochemically distinctive perivascular epithelioid cells. Relatively little is known about the cytopathology of extra-renal PEComas. Because of a considerable range of morphology and their rarity, accurate cytologic classification can be challenging. We evaluated cytologic characteristics and diagnostic pitfalls of extra-renal PEComas on fine-needle aspiration (FNA). Materials and methods: We performed a retrospective search in our cytopathology and surgical pathology database for cases diagnosed as PEComa that had corresponding cytology specimens from 3 medical institutions. All available cytopathology specimens were reviewed. We evaluated cytologic characteristics and recorded histologic diagnoses and immunohistochemical stains. Results: Seven FNA specimens from 6 patients were identified, and cytologic diagnoses were made in all cases as follows: PEComa (4 cases), most consistent with PEComa (1 case), malignant neoplasm (1 case), and hepatocellular carcinoma (1 case). Most specimens were moderately to highly cellular. Cell distribution occurred as tissue fragments with background proliferating capillaries. Most smears were composed of epithelioid cells showing mild to moderate anisonucleosis, abundant eosinophilic cytoplasm, well-defined borders, intranuclear pseudoinclusions, and prominent nucleoli. A combination of myoid and melanocytic markers was expressed in 6 cases except 1 case, which was called hepatocellular carcinoma. Conclusions: This was the largest FNA series for extra-renal PEComas to date. Our study highlights some common cytomorphologic characteristics of PEComa with which cytopathologists should be familiar. In the right clinical and radiologic context, and with the aid of immunohistochemistry, a definitive diagnosis can be achieved.