definition of ovarian cysts
Definition. 1  Ovarian cysts are sacs containing fluid or semisolid material that develop in or on the surface of an ovary. 2  Ovarian cysts are common and the vast majority are harmless. Because they cause symptoms that may be the same as ovarian tumors that may be cancerous, ovarian cysts should always be checked out. The most common types of ovarian cysts are follicular and corpus luteum, which are related to the menstrual cycle.