The two main types of ovarian are: functional ovarian cysts – cysts that develop as part of the menstrual cycle and are usually harmless and short-lived; these are the most common type of ovarian cyst pathological ovarian cysts – cysts that occur due to abnormal cell growth; these are much less common Ovarian cysts can sometimes also be caused by an underlying condition, such as endometriosis. The vast majority of ovarian cysts are non-cancerous (benign), although a small number are cancerous (malignant). Cancerous cysts are more common in women and anyone with ovaries who have been through the menopause.