OBJECTIVETo study the clinicopathologic features and biologic behavior of renal cell carcinoma (RCC) with rhabdoid features.

METHODSTen cases of RCC with rhabdoid features collected during the period from 1995 to 2005 were enrolled into the study. The clinical findings were analyzed and the hematoxylin and eosin-stained sections were reviewed. Immunohistochemistry and electron microscopy were also performed.

RESULTSThe age of patients ranged from 33 to 69 years (mean age = 52 years). Nine of the patients were males and 1 female. Five patients showed evidence of perinephric invasion. Two patients presented with regional lymph node metastases and 1 patient showed distant metastasis to the lung. Histologically, the rhabdoid foci were characterized by loosely cohesive trabeculae, acini, lobules and clusters of rhabdoid cells in otherwise clear cell RCC (9 cases) or papillary RCC (1 case). The rhabdoid cells were round to polygonal in shape and contained globular eosinophilic inclusion bodies in the cytoplasm, eccentric nuclei, vesicular chromatin pattern and prominent nucleoli. Coagulative tumor necrosis was commonly seen. Immunohistochemical study showed that the rhabdoid cells were diffusely positive for CD10 (10/10), cytokeratin AE1/AE3 (10/10), epithelial membrane antigen (10/10) and vimentin (10/10). Focal staining for neuron-specific enolase and S-100 protein was also noted. They were negative for CK7, CK20 and myogenic markers (including myogenin, smooth muscle actin and muscle-specific actin). The mean Ki-67 labeling index of the rhabdoid component was higher than that of the non-rhabdoid component (P < 0.05). Follow-up information was available in 8 patients. While 6 patients are still alive without recurrence, 2 patients died of the disease 6 and 29 months respectively after the operation.

CONCLUSIONSRCC with rhabdoid elements are mainly observed in clear cell RCC and need to be distinguished from oncocytic renal tumors and malignant rhabdoid tumor of kidney. The higher proliferative activity in the rhabdoid areas may indicate more aggressive biologic behavior.