Fat-Predominant Mixed Epithelial Stromal Tumor (MEST): Report of a Unique Case Mimicking Angiomyolipoma

ArticleinInternational Journal of Surgical Pathology 16(1):73-7 · February 2008with10 Reads
DOI: 10.1177/1066896907304523 · Source: PubMed
A unique case of a mixed epithelial stromal tumor (MEST) that was predominantly composed of adipose tissue is reported here. Radiographically and grossly, the lesion was thought to be an angiomyolipoma, based upon its fatty appearance. Microscopically, the lesion was predominantly composed of mature adipose tissue but also contained clusters of bland tubules surrounded by smooth muscle bundles and collagen. By immunohistochemistry, the stroma labeled diffusely for estrogen and progesterone receptors, while the muscle bundles labeled for desmin. Melanocytic markers HMB45 and Melan A, typically positive in angiomyolipoma, were nonreactive. This case expands the morphologic spectrum of MEST to include mimics of angiomyolipoma.
    • "A special variant was also described, containing abundant adipocytes. In these cases, misdiagnosis of the tumor as angiomyolipoma, both in imaging studies and in histology, is likely; however, RESTs do not express melanocytic markers diagnostic for AML [501]. Immunohistochemically, the usual epithelial markers are positive in the epithelial lining and the spindle cells are positive for vimentin, desmin, α-inhibin, calretinin and CD34. "
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