Rhabdoid morphology in renal cell carcinoma (RCC) may, like sarcomatoid change,be perceived as a type of dedifferentiation, and is a poor prognostic factor. Histologically,rhabdoid neoplastic cells are round to polygonal cells with globular eosinophiliccytoplasmic inclusions and eccentric vesicular nuclei and enlarged nucleoli.All types of RCC, including clear cell, papillary, chromophobe, collecting ductcarcinoma, renal medullary carcinoma, acquired cystic disease-associated RCC,ALK-positive renal cancer and unclassified RCC, may display a variably prominentrhabdoid phenotype. Immunohistochemically, the cytoplasm of rhabdoid cellsshows positivity for vimentin and/or cytokeratin. Ultrastructurally, cytoplasmicwhorls/aggregates of intermediate filaments correspond to light microscopicallyobserved inclusions. Genetically, a previous report suggests that combined loss ofBAP1 and PBRM1 may be associated with rhabdoid morphology. As with sarcomatoidchange, pathologists should describe, estimate and state the proportion oftumor cells with a rhabdoid phenotype in the routine pathology report of RCC.
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