Fibroadenoma

What is a fibroadenoma?

Breasts are made up of lobules (milk-producing glands) and ducts (tubes that carry milk to the nipple), which are surrounded by glandular, fibrous and fatty tissue. Sometimes tissue will grow over a lobule like a ball, forming a solid lump. This is a fibroadenoma.

Fibroadenomas are benign and don’t increase the risk of developing breast cancer. They are thought to occur due to an increased sensitivity to the female hormone oestrogen.

A fibroadenoma usually has a smooth rubbery texture. As they move easily under the skin they are sometimes called a breast mouse. Fibroadenomas are usually painless, but some people may feel some tenderness.

Fibroadenomas are very common and it is not unusual to have more than one. Often developing during puberty, they are mostly found in young women, but can occur at any age.

Most fibroadenomas are about 1 to 3cm in size. When more than 5cm they’re called giant fibroadenomas. While fibroadenomas found in teenage girls are called juvenile fibroadenomas.

Most fibroadenomas stay the same size. Some get smaller and some eventually disappear over time. Infrequently, fibroadenomas get bigger, particularly in teenage girls and pregnant and breastfeeding women. This is quite normal and nothing to worry about.

How are they diagnosed?

Fibroadenomas usually become noticeable as a lump in the breast. Your GP will note the lump and refer you to a breast clinic for testing.

A triple assessment of testing will reveal a definite diagnosis. These are a breast examination, a mammogram or ultrasound scan, and a fine needle aspiration (FNA) or core biopsy.

If you are under 35, you’re more likely to have an ultrasound scan rather than a mammogram. This is because younger women’s breast tissue is often too dense to give a clear mammogram image.

Fibroadenomas are often easier to identify for women under 25. If you are in this age group, your fibroadenoma may be diagnosed by examination and ultrasound only. However, if there is any uncertainty, an FNA or core biopsy can be done.

Follow up or treatment

In most cases you won’t need any follow up or treatment if you have a fibroadenoma. Usually you’ll only be asked to go back to your GP or the breast clinic if it gets bigger or becomes painful.

Sometimes fibroadenoma larger than 3cm are surgically removed if you would prefer it. 

Removing a fibroadenoma requires a small operation under local or general anaesthetic. You’ll have a small stitched wound, and your doctors will tell you how to care for it afterwards. The operation will leave a small scar but this will fade in time.

Removing a fibroadenoma doesn’t usually affect the shape of the breast, as normal breast tissue will fill the space where it used to be.

A vacuum assisted biopsy (mammotome) can remove small fibroadenomas without surgery by using a mammogram or ultrasound scan as a guide, small amounts of breast tissue are sucked up through a needle until the lump is seen to disappear.

What this means for you

Having a fibroadenoma does not increase your risk of developing breast cancer. However, it is still important to be breast aware and go back to your GP if you notice any further lumps or other changes in your breasts.