Renal cell carcinoma with rhabdoid-like features lack intracytoplasmic inclusion bodies and show aggressive behavior

In renal cell carcinoma (RCC), tumor cells with rhabdoid features are characterized by eccentric nuclei, prominent nucleoli, and eosinophilic cytoplasm with intracytoplasmic inclusion bodies. In RCC, tumor cells have also been observed resembling rhabdomyoblasts or rhabdoid but without intracytoplasmic inclusion bodies, and here, we defined these rhabdoid-like features of these cells. To this end, we studied a series of clear cell RCC (ccRCC) with rhabdoid features and compared them with a series of ccRCC with rhabdoid-like features to clarify the differences in the immunohistochemical profile and biological behavior. From 695 cases of ccRCC (80.8% of all RCCs), 18 cases with rhabdoid features (2.1% of all RCCs) and 25 cases with rhabdoid-like features (2.9% of all RCCs) were investigated. The 5-year survival rate for ccRCC with rhabdoid features was 44.7% and for ccRCC with rhabdoid-like features 30.3%. Although ccRCC with rhabdoid features showed immunohistochemical co-expression of epithelial markers and vimentin as seen in malignant rhabdoid tumors, ccRCC with rhabdoid-like features showed no such co-expression. Multivariate analyses of cancer-specific survival revealed that perinephric tissues invasion was an independent prognostic factor in ccRCC with rhabdoid features (p = 0.0253) but not in ccRCC with rhabdoid-like features. In summary, although their prognosis is similar, the marker profile and pattern of extension of ccRCC with rhabdoid-like is different from that of ccRCC with rhabdoid features. Therefore, ccRCC with rhabdoidlike features should be distinguished from ccRCC with rhabdoid features.