One generally accepted definition of an ovarian cyst is: ‘a fluid-containing structure more than 30 mm in diameter’.

Cystic lesions in the postmenopausal ovary should only be reported as ovarian cysts, and considered significant, if they are 1 cm or more in size.

Cystic lesions smaller than 1 cm are clinically inconsequential and it is at the
discretion of the reporting clinician whether or not to describe them in the imaging report as they do not need follow-up.