Primary cutaneous perivascular epithelioid cell tumor: A clinicopathological and molecular reappraisal

Primary cutaneous perivascular epithelioid cell tumor (PEComa): Five new cases and review of the literature

“…Prior studies by Liegl et al and Mentzel et al found expression of smooth muscle markers in only 50% (5/10) and 57% (4/7) of cases, respectively . Charli‐Joseph et al reported desmin expression in only 1 of 8 cases in their series, and they stated that MSA and calponin were “variable and unreliable.” Although their series found SMA staining in 7 of 8 cases, less than 5% of cells in each case stained positively for SMA and these positive cells were directly adjacent to small capillary vessels making it difficult to distinguish if these were truly neoplastic cells or merely admixed pericytes expressing SMA . In our present series of 5 cases, 1 case showed patchy SMA and desmin expression, 3 cases were negative for actins and desmin, and 1 case did not have myogenic markers performed (block not available).…”

“…When similar lesions arise in the skin, they are referred to as primary cutaneous PEComas. First described in 2003 by Crowson et al, these lesions are rare . Herein we describe 5 additional cases of primary cutaneous PEComa (Table ) and provide a review of the literature.…”

Primary clear cell sarcoma of the head and neck: a case series with review of the literature

“…PEComas also typically show low‐grade nuclear atypia with small nucleoli, although confusion with both clear cell sarcoma and melanoma may arise when PEComas with malignant histology are encountered. While PEComas usually express melanocytic markers such as HMB45, they also usually express smooth muscle actin and are typically negative for S100 protein and SOX10 . Epithelioid malignant peripheral nerve sheath tumor can also have a nested architecture with strong and diffuse staining for S100 protein, but these tumors more often show a multilobulated growth pattern, moderate to severe cytologic atypia and lack expression of melanocytic markers .…”

Incidence of mature adipocytic component within cutaneous smooth muscle neoplasms

“…The rare cutaneous examples that have been reported are often poorly circumscribed and composed of sheets of epithelioid cells with pale to granular cytoplasm, vesicular nuclei and distinct nucleoli. Although a prominent ‘lacy’ fine vascular component may be noted in the background, the thick vessels and mature adipocytes seen in classic AML are not usually present. As smooth muscle tumors and AML/PEComa have different criteria for malignancy, at least in the kidney, the distinction is potentially important .…”

“…The smooth muscle component of AML usually displays a characteristic pale/clear and/or granular cytoplasm that is typical of perivascular epithelioid cell tumors (PEComas), a unique family of soft tissue tumors with both smooth muscle and melanocytic differentiation of which AML is a member. Accordingly, AML and other members of the PEComa family usually demonstrate a characteristic immunophenotype with co‐expression of actin and/or desmin (myogenic markers) and HMB‐45 and/or MART‐1/Melan‐A (melanocytic markers) . PEComas are exquisitely rare in the skin.…”