Clear cell adenocarcinoma arising out of endometriosis of the urinary bladder is a rare entity. The published literature has a dearth of information about this entity and its histogenesis. In the present case review we present a 59-year-old patient who was treated with robotic anterior pelvic exenteration and ileal conduit. The initial biopsy of bladder tumour purported a high-grade urothelial carcinoma, however the final specimen revealed a clear cell adenocarcinoma arising in endometriosis without any urothelial cancer. Early case reports refer to these lesions as mesonephric or mesonephroid adenocarcinomas but the current WHO nomenclature classifies them under nonurothelial epithelial neoplasms as clear cell adenocarcinomas. Here, we review the literature and discuss their origins. © 2013 Anticancer Research.