What causes breast changes?


Most breast changes are not due to breast cancer.

Some of the common causes of breast changes are listed below.

Hormonal changes

Hormonal changes may cause a woman’s breasts to feel swollen, painful or tender at different times in the menstrual cycle. These changes are not a sign of breast cancer and usually don’t require treatment.

Treatments are available for hormonal breast pain if needed. See a doctor for more information.


A cyst is a fluid-filled sac. Breast cysts are common in women aged 35 to 50 and in women who are taking hormone replacement therapy.

Simple cysts are not cancer and do not change into cancer. However, in rare cases, cysts may have a cancer growing within them or close to them. These changes can be seen on an ultrasound, or found after a cyst is aspirated or drained. 

Many women have a cyst or a number of cysts without knowing it, and these do not usually require treatment. Some women first detect their cyst as a painful lump and they may decide to have it drained if it’s painful or troublesome. This is done by inserting a fine needle into the cyst to draw out the fluid, and is usually a simple and fairly painless procedure.


A fibroadenoma is a smooth, firm breast lump made up of fibrous and glandular tissue. The term ‘breast mouse’ is also used to refer to a fibroadenoma.

We do not know what causes fibroadenomas. They are more common in younger women and may become tender in the days before a period or grow bigger during pregnancy.

Fibroadenomas are not cancer and they do not always need to be removed. If they are removed however, the operation is relatively simple. A general anaesthetic is usually required.