👉 A cystadenoma is a type of benign tumor that is often found in the lining of the kidneys, bladder, and ureters. It is characterized by the development of small, round, and irregular structures, called cysts or nodules, which can be either solid (bigger than a pea) or fluid-filled. These tumors are typically located in the middle third of the kidney, but they can also occur at other locations, such as the bladder or ureters. Cystadenomas