Every woman who ovulates makes a “cyst” every month – a follicle that usually ruptures and then disappears. Cysts can be physiological (functioning cysts) or pathological (benign or malignant).

Ovarian cysts are a common reason for gynaecological referral.

The simplest functional cysts are either follicular cysts or luteal cysts. Follicular cysts occur where the developing follicle does not rupture and grows beyond 3 cm. Luteal cysts arise when the corpus luteum becomes cystic. Functional cysts are more common at menarche and in the menopause transition, in the users of progestogen only contraception or in the presence of gestational trophoblast disease. They are classified by the cells from which they originate (Table 12.1).