High Grade Neuroendocrine Carcinoma/Small Cell Carcinoma

This research study is studying a combination of drugs as a possible treatment for rare genitourinary malignancies among four cohorts, bladder or upper tract carcinoma with variant histology, adrenocortical carcinoma, other rare genitourinary carcinomas and any genitourinary carcinoma with neuroendocrine differentiation. Given preliminary results, the study is being tested in additional patients with bladder or upper tract carcinoma with variant histology at this time while the adrenocortical carcinoma, other rare genitourinary malignancies arms have closed to accrual -The names of the study drugs involved in this study are: * Nivolumab * Ipilimumab