Adult renal cell carcinoma with rhabdoid differentiation: incidence and clinicopathologic features in Chinese patients.

Renal cell carcinoma (RCC) with rhabdoid differentiation is a recently described variant of RCC, which has seldom been reported in China. This form of differentiation has been generally associated with a poor prognosis and is often present in tumors with a poorly differentiated morphology. The development of a rhabdoid morphology appears to represent a common dedifferentiation pathway for renal parenchymal malignancies. The aim of this study is to evaluate the incidence and clinicopathologic features of RCC rhabdoid differentiation in Chinese adult patients and to further investigate its origin. We reviewed 723 cases of RCC obtained between January 2012 and March 2014 in Peking University First Hospital. From these cases, 10 (1.4%) were found to have areas of classic rhabdoid morphology. Immunohistochemistry for vimentin, cytokeratin (CK) (pan-cytokeratin (AE1/AE3), CK20, CK5/6, CK7, and CK8/18), RCC, CD10, Pax-2, Pax-8, CD117, desmin, muscle-specific actin, CD68, p53, and Ki-67 was performed in each case using the labeled streptavidin-biotin method. Rhabdoid differentiation was identified in association with clear cell RCC, papillary RCC (II type), and sarcomatoid RCC. We compared the morphologic and immunohistochemical features between rhabdoid and nonrhabdoid components. In our cases, rhabdoid differentiation was characterized by the presence of cohesive large epithelioid cells with abundant pink cytoplasm and central eosinophilic intracytoplasmic inclusions and 1 or more large, oval, eccentric, or irregular nuclei containing prominent nucleoli. Most of the rhabdoid areas showed a solid growth pattern. In our series, RCC with rhabdoid differentiation had an aggressive biological behavior, and rhabdoid components were most likely associated with high-grade tumors of advanced stage. In all cases, the rhabdoid and nonrhabdoid tumoral areas without sarcomatoid differentiation exhibited the very similar immunophenotype as follows: vimentin (+/-), AE1/AE3 (+), CK8/18(+), CK7(+/-), CK5/6 (-), CK20 (-), RCC (focal +), CD10 (focal +), Pax-2 (+), Pax-8 (+), CD117 (+/-), desmin (-), muscle-specific actin (-), and CD68 (-). On p53 and Ki-67 immunohistochemistry, the positive rate of rhabdoid cells for both p53 and Ki-67, similar to sarcomatoid cells, was higher than that of nonrhabdoid tumor cells without sarcomatoid differentiation. Our results indicate that the incidence rate of rhabdoid differentiation in Chinese adult RCC patients is lower than that of foreign reports. We support that the rhabdoid and nonrhabdoid tumor cells originate from the same clone, and the rhabdoid components present high proliferative activity and indicate a poor prognosis.