A rare, benign (not cancer) kidney tumor made up of fluid-filled cysts. Cystic nephroma can occur in one or both kidneys. Signs and symptoms may include pain in the abdomen or back, a lump in the abdomen, blood in the urine, urinary tract infection, anemia, and fever. Cystic nephroma usually occurs in young children or middle-aged adults. Cystic nephroma may also be found in patients who have pleuropulmonary blastoma (a rare, fast-growing cancer that forms in the tissues of the lung and chest cavity). Some patients with cystic nephroma have a mutation (change) in a gene called DICER1.