Fig. 6.

Primary malignant cutaneous perivascular epithelioid cell tumor (PEComa): clinical presentation and hematoxylin-and-eosin-stained pathology presentation. A 43-year-old man who had worked as a welder for several years presented with a tumor of 5 months’ duration (that had grown from a small, raised area to its current size over a period of 3 months) on the extensor surface of his distal left forearm just proximal to the wrist (A). The neoplasm was a painless, flesh-colored, exophytic scaly nodule measuring 10 × 10 × 5 mm, with a surrounding collarette of epithelium and central ulceration; the initial clinical impression was a keratoacanthoma (a variant of squamous cell carcinoma). Lower (B) and higher (C) magnification views of the microscopic examination of the excisional biopsy show ulceration of the epidermis, crust, and a collarette of epithelium extending from the epidermis into the dermis and surrounding a dermal tumor predominantly consisting of epithelioid cells (most with clear cytoplasm and some with foamy cytoplasm) and numerous capillaries; in addition, spindle tumor cells are present at the tumor periphery, and there are some multinucleated tumor cells. The tumor is classified as malignant based upon the presence of two high-risk, worrisome features: increased mitotic activity (with three mitoses per ten high-power fields) and scattered nuclear pleomorphism (demonstrated by high-grade nuclear atypia) (hematoxylin and eosin: B, × 2; C, × 20). Republished from [96] with permission from the University of California, Davis Department of Dermatology, Sacramento, California