Causes of breast lumps

Most breast lumps are caused by benign (non-cancerous) conditions, although occasionally a breast lump can be a symptom of breast cancer.

It's important to see your GP as soon as possible if you notice a lump in your breast so they can refer you for tests to confirm the cause.Most benign breast lumps are harmless and may not necessarily require any treatment.


Fibrocystic breast disease, also known as fibroadenosis, is a term used to describe a group of benign conditions that affect the breast. The symptoms of fibroadenosis can include:

  • Mastalgia (mastalgia or mastodynia)
  • increase in breast size
  • lumpiness of the breast (nodularity), particularly just before or during a period

Fibroadenosis can develop in one or both breasts, or can affect just part of one breast. The symptoms can also vary significantly between women, with some women finding them slightly annoying and others finding them very painful. The pain and lumpiness will usually disappear after your period.

The cause of fibroadenosis is not well understood. However, it may be the result of the breast tissue responding abnormally to hormonal changes that occur with the menstrual cycle.


Fibroadenomas are smooth, well-rounded solid lumps of tissue that sometimes develop outside the milk ducts (the tiny tubes in the breast that carry milk). They are particularly common in young women.

Theyare sometimesdescribed as"breast mice" because they can easily move around within the breast.

Fibroadenomascan disappear on their own, but they sometimes remain and grow larger, particularly during pregnancy. They don't usually resolve after your period.

It's not clear what causesfibroadenomas, but it is thought they mayoccur because of anabnormal response to the hormone oestrogen. This is becausethey are common in women who haven't been through the menopause and postmenopausal women who are having hormone replacement therapy (HRT) .

Breast cysts

Breast cysts arefluid-filled sacs that develop within the breast tissue and can cause smooth, firm lumps to develop. They are more common in women aged 30 to 60.

Cysts vary in size. Some can be tiny, while others can grow to several centimetres in diameter. Single or multiple cysts can occur in one or both breasts.

Cysts often do not cause any symptoms, although some women may experience pain in addition to any lumps.

As withfibroadenomas, hormones are thought to play a role in the development of breast cystsbecause they are particularly common in pre-menopausal women and postmenopausal women having HRT.

Breast abscesses

A breast abscess is a painful collection of pus that forms inside the breast.

In addition to a painful lump, symptoms of a breast abscesscan include a high temperature (fever) and inflammation (redness and swelling) of the skinover the affected area.

Most breastabscesses are caused by a bacterial infection. The bacteria usually enter the breast through small cracks or breaks in the skin of the nipple, which can sometimes develop during breastfeeding.

Other benign causes

Other benign causes of breast lumps include:

  • mastitis where breast tissue becomes painful and inflamed
  • fat necrosis a hard, irregular lump often caused by trauma or bruising to the breast; for example, after surgery on the breast
  • a lipoma afatty growth that causes a lump
  • an intraductal papilloma awart-like growth in a milk duct, which may also cause nipple discharge

Breast cancer

Although the vast majority of breast lumps are benign, a lump in one of the breasts can sometimes be a sign of breast cancer in women and breast cancer in men .

A lump is more likely to be a sign of breast cancer if it:

  • is clearly defined
  • feels firm
  • doesn't move around
  • persists afteryour period or develops after the menopause (in women)

Breast cancer can also cause some other symptoms, such as discharge from your nipples, dimpling on the skin of your breasts, and changesin the appearance of your nipple (such as becoming sunken into your breast).

The risk of breast cancer increases with age, but is most common in women and men over the age of 50. Havinga family history of the condition may also mean your risk is increased.

and symptoms of breast cancer in men .

Content supplied by the NHS Website

Medically Reviewed by a doctor on 29 Jun 2016