Breast Lumps

Breast lumps are a worry at any time, but can be very common when breastfeeding, particularly lumps that come and go. Reasons for more persistent lumps include engorgement, a blocked duct, and mastitis. If engorgement or mastitis are not treated promptly this could lead to a breast abscess. Lumps in the armpit can also be associated with breastfeeding because breast tissue extends into the armpit. Other possibilities include a benign tumour (fibroma), milk-filled cyst (galactocele) and rarely, inflammatory breast cancer. Check with your health professional about any lump that doesn’t disappear after a week or so, or that you have any concerns about.

As a breastfeeding mother, you can expect lumpy breasts, and you’ll get to know your breasts better than you ever did before.

The lumps will shift location and change, getting larger and smaller as your breast empties and fills. Lumps that come and go are not a cause for any concern. If there’s a particular lump that is persistently there, it may require some investigation.

Breast lumps and medical tests

Persistent breast lumps may need medical investigation to determine their cause. In most tests e.g. ultrasound, mammogram, CT scan, MRI scan, needle biopsy and core biopsy; breastfeeding need not be interrupted. The article Medical Tests While Breastfeeding provides more information and further reading about the compatibility of various tests while breastfeeding.

Common causes of breast lumps while breastfeeding


Some engorgement (full tender breasts) when your milk first comes in and in the first few weeks can be quite normal, but swollen lumpy breasts at other times may mean your baby isn’t draining the milk from all areas of the breast. Contact your IBCLC lactation consultant or breastfeeding helper to find the cause of your engorgement and see Engorged Breasts for further help.

Blocked milk duct

A blocked or plugged milk duct prevents milk flowing freely in an area of the breast and may lead to engorgement. See Blocked Milk Duct for causes and treatment ideas.


If engorgement or blocked ducts are not relieved promptly a mother may get symptoms of mastitis—inflammation of the breast. This will be very painful and may cause mum to feel generally unwell with flu type symptoms such as feeling achey and shivery. Left untreated, mastitis may be associated with an infection requiring antibiotics. See Mastitis Symptoms and Treatment for further information to prevent and treat mastitis.

Breast abscess

An abscess will usually be felt as a painful, swollen lump inside the breast, and a mother may have a high temperature. The abscess is a pocket of pus and is more likely to develop following painful engorgement or mastitis that wasn’t treated promptly. For more information about diagnosis and urgent treatment see Do I Have a Breast Abscess?

What is a galactocele?

A galactocele is a harmless, milk filled cyst. It’s a lump that feels like a smooth, round, moveable sac inside the breast. It is a section of a milk duct where the contents have gradually developed the consistency of butter or oil. It is not usually painful or tender. A diagnosis can be made by ultrasound or by taking a little sample of the contents of the cyst (by fine needle aspiration). The cyst will disappear when breastfeeding ends.

The presence of a galactocele is compatible with breastfeeding. If surgery is required, breastfeeding does not need to be interrupted. Case reports suggest that increased rates of galactoceles are observed after breast augmentation (Chun & Taghinia, 2009; Lin et al., 2008; Acarturk et al., 2005).

For further information about diagnostic tests and the radiological appearance of a galactocele see Galactoceles (, Steven Halls, 2016).

Lumps in the armpit?

Breast tissue extends into the armpit and it has a special name “The Tail of Spence”. During engorgement, for example when your milk first comes in, you may notice lumps and swelling in your armpits. Use the tips in Engorged Breasts to reduce this engorgement. It is also possible to have extra breast tissue that is not connected to the breast both in the armpit and in other areas of the body.  Again this ‘accessory’ breast tissue may become engorged when your milk first comes in. For more information about these types of swelling when breastfeeding, see Kelly Bonyata’s article below.


Rare causes of breast lumps while breastfeeding

Breast cancer

It is very rare for a lump to be a sign of cancer especially while you are breastfeeding but always get medical advice if the lump is still there after a week 1, and particularly if it is getting bigger, does not move, is firm and hard, or if there is dimpling of the skin.

Most women worry that they may have cancer when they discover a breast lump. Studies have shown that breastfeeding reduces a mother’s risk of breast cancer. However, a lump that does not go away after a week or recurs in the same place despite careful treatment for a blocked duct, needs checking. In many cases breast lumps are benign tumours (fibromas) or milk-filled cysts (galactoceles) which can be diagnosed and treated whilst you continue to breastfeed. It is very rare for a lump to be a sign of cancer. But do consult your doctor, especially if the lump continues to grow, does not move, or is firm and hard, and if there is dimpling of the skin.

Inflammatory carcinoma of the breast

Inflammatory breast cancer is a rare type of breast cancer where the whole breast can look red and inflamed and be very sore. Jack Newman, Canadian paediatrician and breastfeeding expert explains:

This type of cancer can occur at any age but it is uncommon. It is a particularly aggressive type of breast cancer and sometimes the mastitis-like symptoms can come on over a day or two. The breast may swell rapidly and be quite red. A hint that this is different from typical mastitis is that the skin may have a peau d’orange (orange peel) appearance. Sometimes the nipple is retracted as well.


Breast lumps that come and go in the breasts or even the armpits are not unusual when breastfeeding. Possible causes of breastfeeding related lumps include engorgement, blocked ducts, mastitis, and galactoceles. It is rare for a lump to be a breast abscess or a sign of cancer but it is important to get medical advice if the lump is still there or increasing in size after about a week to rule this out. Most diagnostic tests are compatible with breastfeeding.

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