title: Retroperitoneal sclerosing PEComa with melanin pigmentation and granulomatous inflammation-a rare association within an uncommon tumor.
abstract: 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.
authors.affiliation: Department of Pathology, Tata Memorial Hospital, Parel, Mumbai, India.
authors.forename: Bharat
authors.initials: B
authors.lastname: Rekhi
authors.forename: Mukund
authors.initials: M
authors.lastname: Sable
authors.forename: Sangeeta B
authors.initials: SB
authors.lastname: Desai
mesh_terms: D000951:Antigens, Neoplasm / Q000032:analysis; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000473:pathology; D008543:Melanins / Q000032:analysis*; D008853:Microscopy; D008875:Middle Aged; D054973:Perivascular Epithelioid Cell Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D010858:Pigmentation; D011860:Radiography, Abdominal; D012186:Retroperitoneal Neoplasms / Q000175:diagnosis* / Q000473:pathology*
chemical_list: D000951:Antigens, Neoplasm; D008543:Melanins