Breast lump - Causes 

There are several different causes of benign (non-cancerous) lumps and breast pain, including the following:

• mastitis (inflammation of the breast): this can be either breastfeeding mastitis or non-breastfeeding mastitis
• nipple discharge (galactorrhoea)
• dilated milk ducts: milk ducts are the tiny tubes in your 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, and is most common in pre-menopausal women (women who are still having periods)
• a fibroadenoma: a small tumour (growth) in the breast that is more common in young women, such as those in their twenties
• a cyst (fluid-filled lump): these are most common in pre-menopausal women and those who take hormone replacement therapy
• fat necrosis: a hard, irregular lump that is often caused by trauma or bruising to the breast, for example, following breast-reduction surgery
• a lipoma: a fatty growth that causes a lump
• a 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 that is not associated with your menstrual cycle is sometimes referred to as non-cyclical breast pain.

Hormones

Hormonal changes are the most common cause of benign breast lumps. Hormones are chemicals that are 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 that is used to replace the female hormones that a woman’s body is no longer producing because of the menopause