Clear cell papillary renal cell carcinoma and clear cell renal cell carcinoma arising in acquired cystic disease of the kidney: an immunohistochemical and genetic study.

Clear cell papillary renal cell carcinoma (RCC) is a recently established disease entity. However, there are few reports on genetic study of this entity. We report such a case with focus on genetic study. A 57-year-old Japanese man was found to have 3 renal tumors. Histologically, two tumors showed findings of clear cell RCC; and the other tumor showed findings of clear cell papillary RCC that was characterized by papillary growth pattern of neoplastic cells in cystic space with purely clear cell cytology. Immunohistochemically, tumor cells of clear cell papillary RCC were diffusely positive for PAX2 and cytokeratin 7, but negative for CD10, RCC Ma, and AMACR. In fluorescence in situ hybridization study for one clear cell papillary RCC, we detected polysomy for chromosome 7 and monosomy for chromosomes 17, 16, and 20. In addition, we detected mutation of VHL gene in clear cell RCC, but found no VHL gene mutation in clear cell papillary RCC. Finally, our results provide further evidence that clear cell papillary RCC may be both morphologically and genetically distinct entity from clear cell RCC and papillary RCC.