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Case of the Week #359
A 26 year old woman presented with a 4.0 cm renal mass.
What is your diagnosis?
Angiomyolipoma with epithelial cysts (AMLEC)
Histology shows three components: (a) epithelial cysts lined by cuboidal to hobnail cells; (b) compact subepithelial Müllerian-like AML stroma with admixed chronic inflammation and (c) muscle predominant AML with dysmorphic blood vessels exterior to the subepithelial stroma (Diagn Pathol 2007;2:11). Immunostains show that the subepithelial stroma stains most intensely with HMB45 and MelanA, as well as ER, PR and CD10. The muscle predominant AML areas stain most intensely with smooth muscle actin and desmin. The cyst lining stains for pancytokeratin, but is negative for HMB45, MelanA, ER, PR and CD10.
The differential diagnosis includes mixed epithelial stromal tumor / MEST. However, MEST occurs almost exclusively occurs in perimenopausal women with obesity or receiving exogenous hormones, or men treated with lupron or DES. It lacks the distinctive dysplastic blood vessels and disorganized exterior muscular layer of AML, and has a different immunohistochemical profile.
AMLEC typically has benign behavior.
Nat Pernick, M.D., President
and Shivani Thakore, Associate Medical Editor
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