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 possible causes of lumps include milk-filled cysts (galactoceles), benign cysts and tumours (fibroadenomas), and rarely, breast cancer or 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. For 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, further reading and references 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 cause local pain and a lump or 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 antibiotic treatment. 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?


A galactocele is a harmless, milk filled cyst. It is a section of a milk duct where the milky contents have gradually developed a thicker, creamier consistency like butter or oil. The lump feels like a smooth, round, moveable sac inside the breast. It is not usually painful or tender but may sometimes be uncomfortable. Squeezing the galactocele may cause milk to be expressed from the nipple 1. A diagnosis can be made by a breast ultrasound2 or by taking a little sample of the contents of the cyst by fine needle aspiration. Occasionally a galactocele may become infected and need draining but usually the cyst will disappear when breastfeeding ends3.

Galactoceles are thought to be caused by the blockage of a milk duct. The cyst may be aspirated [drained] to avoid surgery, but will fill up again. It can be removed surgically under local anaesthesia without stopping breastfeeding.


For further information about diagnostic tests and the radiological appearance of a galactocele see Galactoceles (, Steven Halls, accessed June 2018).

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 but should resolve after a week or two. For more information about these types of swelling when breastfeeding, see Kelly Bonyata’s article below.


Lactating adenoma

A lactating adenoma is a painless benign tumour appearing in the breast during late pregnancy or during breastfeeding4. They can grow rapidly due to hormonal stimulation and disappear spontaneously when breastfeeding ends5.


A phlegmon is an area of inflammation in the ducts associated with recent or ongoing mastitis (ABM Protocol #30).

Breast lumps unrelated to breastfeeding

Breast cysts and fibroadenomas

Examples of benign (non cancerous) breast lumps include breast cysts (fluid filled lumps) and fibroadenomas (solid lumps). Cysts and fibroadenomas within the glandular or milk making tissue could have the potential to impede milk flow or cause a blockage in an area of the breast. If an area of the breast cannot drain it will begin to shut down milk production in that area of the breast. Occasionally depending on the symptoms, size and position of the cyst or fibroadenoma a mother may decide to stop breastfeeding on one breast while continuing on the other side.

The problem with adenomas is that they can cause blockages and impairments to normal breast function, and they can also be a sign of hormonal imbalances.

Lawrence and Lawrence say that cysts should be removed and biopsied but won’t interfere with breastfeeding. They add that pregnancy and breastfeeding can stimulate the growth of fibroadenomas that are related to the menstrual cycle. NICE guidelines discuss diagnosis techniques and treatment options for symptomatic breast fibroadenomas including high-intensity focused ultrasound6, and see Fibroadenoma of the Breast (Steven Halls) for more reading.

Fibrocystic breasts

Fibrocystic breast condition (previously called fibrocystic breast disease) is a benign breast condition that encompasses a group of symptoms in the glandular breast tissue such as breast pain, solid lumps and cysts (fluid filled sacs) 7. Some authors advise reducing caffeine in the mother’s diet to improve symptoms 8 or taking vitamin E supplements 9. Lawrence and Lawrence report that fibrocystic breasts can be associated with a bloody discharge from the nipple during pregnancy and lactation but generally the syndrome is not a contraindication to breastfeeding.

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 10, 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. This could occasionally be mistaken for mastitis. 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.

This article should not be construed as medical advice. Always confirm the nature of persistent breast lumps with your medical professional.