Prognostic Significance and Nature of Rhabdoid Features in Renal Cell Carcinoma

Background: Recent reports have indicated that renal cell carcinoma (RCC) with rhabdoid features follows an aggressive clinical course. We investigated the prognostic significance and nature of the rhabdoid component. Methods: We retrospectively analyzed the incidence and clinicopathologic characteristics of RCC with rhabdoid features in 174 radical nephrectomy cases. The specimens were examined histologically and immunohistochemically. Results: Twelve of the 174 RCC cases (6.9%) showed rhabdoid features. Histologically, all the tumors with rhabdoid features were of the clear cell type. The presence of rhabdoid features was significantly associated with higher Fuhrman's nuclear grade and higher pathologic tumor stage at presentation. Among the 12 patients who showed the rhabdoid component, nine (75%) developed metastasis and seven (58.3%) died of disease-related causes. The presence of rhabdoid features was independently associated with metastasis and disease-related mortality. The rhabdoid cells were positive for vimentin; variably positive for pan-cytokeratin, epithelial membrane antigen, and CD10; and negative for cytokeratin 7, smooth muscle actin, desmin, E-cadherin, and c-Kit. No case showed loss of integrase interactor-1; one was p53 positive, and five were insulin-like growth factor mRNA binding protein 3 positive. The Ki-67 labeling index was 1-25% (mean, 5.5%). Conclusions: The rhabdoid component is an independent prognostic factor for metastasis of RCC; therefore, identification of this component is critical.