Clear cell renal cell carcinoma with focal renal angiomyoadenomatous tumor-like area.

Recently, renal angiomyoadenomatous tumor (RAT) has been identified. However, there are no descriptions about clear cell renal cell carcinoma (RCC) with focal RAT-like features. A 33-year-old Japanese man was found to have a tumor in the left kidney. Macroscopically, the tumor extended into the perinephric fat tissue, and the cut surface showed the yellowish color. The histologic examination of the tumor consisted of 2 components of clear cell RCC and RAT-like area. The RAT-like area showed the admixture of epithelial cells with basophilic or clear cytoplasm and stromal component containing leiomyomatous stroma, fine capillary network, and pericytic network. Immunohistochemically, epithelial neoplastic cells in RAT-like area were diffusely positive for CD10 and RCC Ma. G-band karyotype showed the structural abnormality of chromosome 3 and both components of clear cell RCC and RAT-like area revealed the identical VHL gene mutation. Finally, pathologists should pay attention to the presence of clear cell RCC focally resembling RAT.