Breast cysts are bubbles of fluid in the breast, similar to a blister. They are benign (non-cancerous) and are common in women aged 35-50. They are also common in women taking hormone replacement therapy. It’s important to know how to recognise breast cysts and what to look out for if you suspect a lump is not benign.

Types of breast cyst

In the breast, fluid is constantly being produced then reabsorbed. When a milk duct becomes blocked or more fluid is produced than absorbed, such as at certain times in a woman’s hormonal cycle, breast cysts may form or get larger.

Most cysts are tiny — only a few millimetres in diameter. They usually develop quickly then stay the same size. If you have a breast cyst, you will often have more than one. Larger cysts can be felt when doing a breast examination and may be either soft or firm and should move easily in the breast.

It is not known why some women experience more breast cysts than others.

Breast cyst symptoms

Many women worry that a cyst is, or will develop into, cancer. Cysts are not dangerous, however, and will not change into cancer. If you ever develop cancer in the same area as a cyst, it won't have been caused by the cyst.

However, if you have breast cysts, they may be painful — particularly before your period. You may also find that they are tender if you press on them. Sometimes even if you can’t feel the cyst, your breast tissue surrounding it may feel tender or painful.

Breast cyst diagnosis

Larger breast cysts can be felt on examination but smaller cysts are often only detected by conducting an ultrasound or a mammogram. On an ultrasound, they look smooth and round, which sometimes makes them hard to distinguish from a solid lump that may need to be investigated further.

It is important to have them looked at further so that you and your doctor can make sure the lump is a harmless cyst.

Breast cyst treatment

Because cysts are harmless, they usually don’t need to be treated. However, if they are painful, you and your doctor may decide to drain them. Your doctor may also recommend draining a cyst that is large enough to be felt, even if it is not painful. This is so you will not have to worry about it, despite it being harmless.

To drain a cyst, the doctor will use a very fine needle. This process may be slightly uncomfortable but if there is any pain, it is usually over quickly. The draining process usually only takes a couple of minutes per cyst. The fluid inside the cyst may be clear or coloured, but this is nothing to worry about either.

When to seek help

It is important to become familiar with the feel of any lumps in your breasts. This is because some lumps may not be cysts and will need to be investigated further. You need to see your doctor if:

• you find a new lump in your breast or armpit
• part of your breast feels thick or swollen
• the skin on your breast is dimpled or irritated
• your nipple is painful, pulled in or has discharge
• there is redness or flaky skin on your breast or nipple
• the size and shape of your breast has changed
• your breast is persistently painful

Resources and support

For more information about breast cysts and changes:

• Download the Breast Changes brochure from the National Breast Cancer Centre.
• Download the Breast Cysts brochure from the Westmead Breast Cancer Institute.
• Phone Breast Cancer Network Australia on 1800 500 258.