24th May 2025

Simple Breast Cyst

Breast cysts represent one quarter of all benign breast lesions. As with fibroadenomas, they can affect women of any age, but are more common in women between the ages of 35 and 50 years. The majority of cysts present as a unilateral, solitary mass and are usually found in conjunction with fibrocystic change.

It is believed that most breast cysts result from hormonal influences and their fluctuating levels, resulting in the blockage of the breast acini and a subsequent fluid-filled dilatation of the duct(s). In particular, cysts tend to become larger and painful around menstruation.

A large proportion of women will remain asymptomatic and may be unaware that they have a cyst. In those that do detect a breast lump, cysts typically present as a painful or painless, round to ovoid mass, ranging from a few millimetres to several centimetres in size. Acute enlargement frequently causes severe, localised pain of sudden onset and is usually associated with hormonal changes. However, cysts tend to stop forming in the postmenopausal period and may regress on their own accord.

Clinical examination usually reveals a smooth, firm, discrete, tender mass with a distinct border, said to resemble a ‘grape’ in texture. As with other benign breast disease, accompanying imaging is usually determined by the patient’s age. Features seen on ultrasound include a round to ovoid, anechoic mass, with circumscribed margins and posterior acoustic enhancement. Mammography typically reveals a round to ovoid mass with circumscribed margins only.

Breast cysts are not associated with an increased risk of malignancy and therefore, treatment is not usually indicated. Larger, more painful cysts may be aspirated to provide symptomatic relief. Cytological analysis of the aspirate is only warranted if there are any concerning features, such as blood-stained fluid. Otherwise, the material is typically discarded.