Patient education • CLINICAL PRACTICE What is a ?

The New South Wales Breast Institute.

A breast cyst is a collection of fluid in a mammogram, they can sometimes be or that show worrying features on the breast. Fluid is being produced and seen as a smooth, round mass in the breast imaging or pathology tests. reabsorbed constantly in the milk ducts tissue. On ultrasound, they are usually a in the breast. When a duct becomes smooth, round, well defined, and black. Can they come back? blocked, or the amount of fluid produced Sometimes cysts do not have these typical Cysts can come back after aspiration, or is greater than the amount absorbed, fluid features and are difficult to distinguish from new cysts can develop in the nearby breast accumulates causing cysts. Cysts can be solid (nonfluid) lesions just by looking, and tissue. Cysts that do come back after single or multiple. They can come and go, require further investigation. These are aspiration usually take several months to and vary during the . When sometimes referred to as ‘complex cysts’. recur. Any that come back within a few cysts become large, they can cause a lump. weeks may require further testing. Classically the lump is smooth, soft, and How are they treated? moves easily. If the fluid is under tension, Cysts causing no symptoms and showing Are they cancerous? it can feel firm when examined. Cysts are typical benign (noncancerous) features on Breast cysts are not cancerous, and often tender. Even if there is no distinct imaging require no treatment. Most cysts having cysts does not increase the risk of lump to feel, the breast tissue containing a fit into this category. Sometimes lesions are developing breast cancer in the future. There cyst or cysts is very tender. seen on imaging that may be cysts (fluid) is a rare condition called 'intra-cystic cancer' but could also be solid, and these require that can develop inside a cyst, but these How common are cysts? further testing with drainage of the cyst cysts usually look unusual on ultrasound and Breast cysts are very common, and (aspiration). This involves inserting a needle behave differently when aspirated. although they can occur in women of any into the cyst, often under the guidance of Women who get a lot of cysts may age, they are more common in the 30–50 ultrasound, to remove fluid from the cyst. become complacent about breast lumps years age group. They usually disappear If the cyst has watery fluid in it, it may and not get lumps checked. This can result after menopause, but in some women they disappear with aspiration. If is has a thick in a delayed diagnosis if breast cancer can last throughout life. Cysts are more pasty or gel-like fluid in it, the cyst may develops. Every new breast lump needs to common in postmenopausal women who not drain completely – but this is not a be appropriately investigated. take hormone therapy compared to those reason for concern. Cysts that are tender are AFP who do not. often aspirated to reduce discomfort. Sometimes a sample of the aspirated fluid is Adapted from: ‘Breast cysts’ fact sheet. How are they diagnosed? sent for testing by a pathologist to confirm The NSW Breast Cancer Institute In most women, cysts are tiny (only a that it is a cyst. www.bci.org.au few millimetres in diameter) and cause Occasionally is recommended no symptoms. Often they are seen on a to remove a cyst. This is very uncommon, mammogram or ultrasound that has and is usually reserved for cysts that keep

✁ been performed for another reason. On coming back after repeated drainage,

Reprinted from Australian Family Physician Vol. 34, No. 4, April 2005 4 257