Clinicopathologic Study of 28 Cases of Tubulocystic Renal Cell Carcinoma: Is It Time to Reclassify It as a Tubulocystic Renal Cell Tumor?

Tubulocystic renal cell carcinoma (TC-RCC) is uncommon and is defined by exclusive tubulocystic growth. Its clinicopathology is still evolving. Twenty-eight cases of so-defined TC-RCC were studied for clinicopathology as well as, in some cases, immunohistochemistry. The study showed the tumor had a male predominance; tumor size ranged from 0.1 cm to 3.5 cm; multifocality and peripheral location were common. More than 1/3^rd of the cases presented with pseudoinvasion into fat; 54% of cases concurred with papillary adenoma(s); 53% of cases concurred with at least one other type of low-grade/indolent renal cell carcinoma. Background kidney displayed end-stage kidney disease in 96% of the cases. The tumor was positive for AMACR, negative for GATA3, and rarely/focally positive or completely negative for CK7 and CAIX. All presented with benign clinical courses. Given its frequent association with end-stage kidney disease and other indolent renal neoplasms as well as its uneventful clinical course, we proposed to reclassify it as a tubulocystic renal cell tumor.