Mostly seen incidentally in radiology or in autopsy.
Clinical: Rare before age of 40; increase with age thereafter.
May be multiple and large in older patients; otherwise, solitary simple cysts (as the name implies!)(image A).
Unilocular cyst with smooth lining and contain clear fluid.
Cyst lined by a flattened or attenuated layer of cells (image B), or may lack an epithelial lining (denuded).
May be surrounded by fibrosis.
Cystic nephroma/mixed epithelial and stromal tumor: Cysts with hobnailed cells + cellular stroma ("ovarian type stroma").
Cystic RCC: Multilocular cyst or partially cystic and lined by clear cells.