Retroperitoneal sclerosing PEComa with melanin pigmentation and granulomatous inflammation-A rare association within an uncommon tumor

• Main Authors: Bharat Rekhi, Mukund Sable, Sangeeta B Desai
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2012-01-01
• Series: Indian Journal of Pathology and Microbiology
• Subjects: HMB45; melanoma; myomelanocytic tumor; PEComa; retroperitoneal sarcomas; sclerosing PEComa; uncommon soft tissue tumors
• Online Access: http://www.ijpmonline.org/article.asp?issn=0377-4929;year=2012;volume=55;issue=3;spage=395;epage=398;aulast=Rekhi

PEComa, defined as a perivascular epithelioid cell tumor, displays a wide clinicopathological spectrum. Lately, a sclerosing PEComa has been identified as its distinct variant, but with limited documentation, in view of its rarity. Herein, we describe an uncommon case of a 53-year-old lady, who was referred to us with pain abdomen. Radiological imaging disclosed a well-defined, hypodense retroperitoneal mass. The excised tumor was a round, encapsulated soft tissue mass measuring 7 cm with a tan-brown cut surface. Microscopy showed uniform, epithelioid cells with clear cytoplasm, focal melanin pigmentation and mild nuclear atypia, arranged in sheets and nests around capillary-sized vessels in a dense sclerotic stroma. Additionally, co-existing epithelioid granulomas were noted. On immunohistochemistry (IHC), tumor cells were diffusely positive for HMB45; focally for desmin and smooth muscle actin (SMA), while negative for EMA, CD10, S100-P, Melan A, CD34, AMACR and CK MNF116. This case reinforces sclerosing PEComa as an uncommon, but a distinct clinicopathological entity and exemplifies diagnostic challenge associated with it; necessitating application of IHC markers for its correct identification. Presence of melanin pigment and granulomatous inflammation in the present tumor constitute as novel histopathological findings in a sclerosing PEComa.