Breast cysts are fluid-filled sacs that form within breast tissue. They are benign breast lumps that are common and harmless and often go away without treatment.

Breast cysts tend to occur most frequently in premenopausal women over the age of 35, and become more common in the time approaching menopause. They can, however, occur in women of any age, including postmenopausal women, especially those who are taking hormone replacement therapy (HRT).

In about a third of women who develop breast cysts, lumps are found in both breasts. They can occur suddenly and some women may have several breast cysts. Many women have them but never notice.

What causes breast cysts?

Breast cysts are formed when breast ducts become dilated and fill with fluid and seem to be linked with oestrogen production. They are one of the most common types of benign breast lumps that form before the menopause, and they become more common as menopause approaches. Breast cysts can develop or change in size at different times of the menstrual cycle, and sometimes appear during or after pregnancy as a result of the filling and emptying of milk ducts.

Sometimes breast cysts are just the result of normal fibrocystic changes that occur during the menstrual cycle, and are due to an overgrowth or swelling of the fibrous tissue that supports the structure of the breasts. This can block up the ducts that normally allow normal breast secretions to drain away.

The extra fluid that collects causes small breast lumps to form. This is a relatively common symptom in many women, who experience feelings of fullness in the upper parts of breasts and lumpy areas that may move and that can be tender.

What do breast cysts feel like?

Breast cysts are typically oval or round masses that are smooth and moveable under the fingers. They can vary in size from very small/unnoticeable to large and painful, and may change during the menstrual cycle. A breast cyst that is unnoticeable most of the time may become large and painful just before a period. Breast cysts near the surface of the breast tissue usually feel soft, while those found deeper in the breast tissue can sometimes feel like hard lumps. They can arise anywhere in the breast, though are most commonly found in the upper half.

Are breast cysts linked to breast cancer?

Breast cysts and other benign breast lumps often feel quite different from cancerous lumps:

  • ● Breast cysts and other benign lumps are usually oval or round, firm or rubbery with smooth edges, and easily moved under the fingers.
  • ● Malignant breast lumps are often hard with a non-uniform shape and irregular edges, and may be fixed to the skin or the chest wall. Breast cancer may also be accompanied by other breast changes such as dimpling of the skin or nipple retraction that are not normally associated with benign lumps or breast cysts.
  • As 90% of malignant tumours are painless, a painful or tender lump in the breast is very likely to be a breast cyst or other benign mass.

Breast cysts and breast cancer risk

Just because you develop breast cysts does not mean that your risk of breast cancer is increased. Family history remains one of the most important breast cancer risk factors.

It is, however, still important for any breast lump to be checked by a specialist who can then decide whether you need further tests or treatment. If you are prone to breast cysts or other benign lumps, it is still very important to remain breast aware, and to do breast self-examination.

If you have had breast cysts in the past and you find a new lump, don’t assume it is another cyst until it has been properly examined and tested as necessary.