Fine-needle aspiration of chromophobe renal cell carcinoma. Analysis of six cases.

Abstract

The chromophobe variant of renal cell carcinoma is a recently described and frequently unrecognized tumor. Because the prognosis of the chromophobe variant appears to be intermediate between that of oncocytoma and the clear cell variant of renal cell carcinoma, accurate diagnosis may be important for appropriate clinical management. A retrospective analysis of fine-needle aspirations of four primary and two metastatic chromophobe renal cell carcinomas (five typical and one eosinophilic variant) with histologically confirmed primary tumors was performed. Hale's colloidal iron stain was strongly positive in a diffuse cytoplasmic pattern in all resected primary tumors. All fine-needle aspirations were characterized by cellular smears comprised of single cells and small groups of cells. The cytoplasm varied from granular to flocculent. A characteristic feature was the presence of occasional markedly enlarged, bizarre, often multinucleated cells, within a background of moderately atypical cells. Nuclear enlargement, hyperchromasia, pleomorphism, and outline irregularity were noted in all cases. These features imparted a koilocyte-like appearance to many of the cells. Intranuclear pseudoinclusions were present in four cases and were numerous in two. Both primary and metastatic chromophobe renal cell carcinomas have unique cytologic features that allow for their distinction from oncocytoma and other variants of renal cell carcinoma.