Breast Lump During Breastfeeding

Breast lumps are a concern at any time and can be very common during breastfeeding.

What are the causes of breast lumps during breastfeeding? 

1. Blocked Milk Duct 

A blocked milk duct leads to trapped milk in the breast tissue, which may form a painful lump. Anything that prevents good breast drainage can cause a blocked duct, such as poor positioning, a tight bra or scarring from previous breast surgery. Frequent breastfeeding, gentle breast massage and warm compresses can help. A blocked milk duct usually resolves within 24 to 48 hours, however, it may progress to mastitis. 

2. Mastitis & Abscess 

Mastitis is inflammation of the breast and affects 10 percent of breastfeeding mums. In addition to a lump, mastitis can cause redness on the breast, fever and chills. Untreated mastitis can result in an abscess, which is a walled-off area of pus and bacteria in the breast. An abscess requires urgent medical attention. Diagnosis is made by ultrasound and treatment involves antibiotics and drainage. 

3. Galactocele

A galactocele is a benign milk-filled cyst. Typically the lump is smooth and painless. Massaging the lump may cause milk to be expressed from the nipple. Diagnosis is made by ultrasound and sometimes by sampling the cyst content. Galactoceles usually disappear when breastfeeding ends. 

4. Benign Breast Lumps  

Benign breast lumps unrelated to breastfeeding, such as cysts (fluid filled lumps) and fibroadenomas (solid lumps), can also occur. 

    5. Breast Cancer  

    Breast cancer is uncommon in women of childbearing age. Breastfeeding women account for only 3 percent of breast cancer cases. However any persistent breast lumps (or changes) after treatment for blocked duct, mastitis or abscess always require investigations.

    Are medical tests safe during breastfeeding? 

    Persistent breast lumps may need further investigations, which are usually compatible with breastfeeding.


    Mammogram and ultrasound are safe to use during breastfeeding. It is recommended that breasts are as empty as possible prior to the test to maximise the quality of the images.  


    A breast biopsy has a small risk of infection and bleeding. In breastfeeding women, there is an additional risk of milk fistula - where there is a constant leakage of milk through a ‘hole’ on the skin of the breast. It is important to continue breastfeeding after a biopsy to avoid a fistula, otherwise, the milk will find the path of least resistance to flow which may be the opening at the biopsy site.

    Lactation Lumps was published in Issue 101 of On the Coast Families Magazine.  

    Related Information

    Breast Cysts