Management of Atypical Renal Cell Carcinomas.

OPINION STATEMENT: Non-clear cell renal cell carcinoma (RCC) encompasses a diverse group of diseases, with research yielding different histologic findings and genetic profiles with each distinct subgroup. Simply mirroring the management techniques of clear cell RCC and borrowing from its growing armamentarium of therapeutic agents, while somewhat productive at first, but will ultimately be limiting. Further investigation into the molecular pathogenesis of disease, similarities and differences between specific subtypes, and mechanisms of resistance to therapeutics will help identify new targets, stimulate development of novel agents, and improve clinical trial offerings for non-clear cell RCC (nccRCC). As nccRCC has been largely excluded from past trials, there will be a need for future trials to be designed either to evaluate nccRCC specifically, or to include nccRCC as a prespecified subgroup. Multi-center collaborative trials should be supported, as many of the nccRCC subtypes are rare and remain underrepresented even within the construct of trials that only enroll nccRCC. Given the absence of clear molecular targets at present, patients with metastatic nccRCC should be offered and encouraged enrollment on clinical studies whenever possible.