Breast lump - Causes 

Causes of breast lumps 

A benign (non-cancerous) breast lump and breast pain can be caused by several different conditions.

These include the following:

  • a cyst (fluid-filled lump) – most common in pre-menopausal women (women who are still having periods) and those undergoing hormone replacement therapy
  • a fibroadenoma – a small lump in the breast more common in young women, for instance those in their twenties
  • mastitis (inflammation of the breast) – this can be either breastfeeding mastitis or non-breastfeeding mastitis
  • nipple discharge (galactorrhoea)
  • dilated milk ducts – milk ducts are tiny tubes in the breast that carry milk
  • trauma to the breast due to injury
  • scarring of the breast from past surgical procedures
  • fibrocystic breast disease (fibroadenosis) – a benign growth in the breast that causes lumpiness and tenderness, most common in pre-menopausal women
  • fat necrosis – a hard, irregular lump often caused by trauma or bruising to the breast, for example, following breast reduction surgery
  • lipoma – a benign fatty growth that causes a lump
  • breast abscess – a painful collection of pus under the skin
  • an intraductal papilloma – a benign growth in a milk duct, which may also cause nipple discharge
  • a haematoma (blood clot)

Breast pain can also sometimes be caused by your menstrual cycle. This is known as cyclical breast pain. Breast pain not associated with your menstrual cycle is sometimes referred to as non-cyclical breast pain.

Read more information about how a breast lump is diagnosed.


Hormonal changes are the most common cause of benign breast lumps. Hormones are chemicals produced by the body and have a wide range of effects. Sometimes changes in the levels of hormones in your body can cause your breasts to feel lumpy or swollen.

Hormonal changes can occur:

  • in teenagers
  • during the monthly menstrual cycle
  • during the menopause, which is when a woman’s periods stop
  • if you take the oral contraceptive pill, which contains artificial versions of female hormones
  • if you take HRT, which is treatment to replace female hormones a woman’s body is no longer producing because of the menopause

Page last reviewed: 07/08/2012

Next review due: 07/08/2014


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