There are two main types of ovarian cysts. Functional ovarian cysts develop as part of the menstrual cycle. These are common, short-lived and usually harmless. Pathological ovarian cysts are much less common and are the result of abnormal cell growth.
Other types of cysts include dermoid cysts (rarely cancerous but can contain tissue such as skin, hair or teeth), cystadenoma (filled with watery or mucous material and grow on the surface of the ovary) and endometrioma (caused by endometriosis).