What Causes Breast Lumps While Breastfeeding?

Breast lumps can appear at any time when you are breastfeeding. There are many reasons for breast lumps and most lumps are of little concern and will simply disappear. Some disappear quite quickly, and others may take some time to resolve. Other lumps may need treatment.

Key takeaways:
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    See your PCP if you have a fever for more than 24 hours.
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    Prompt evaluation of any concerning breast lumps during breastfeeding is key.
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    Offering the other breast can reduce the engorgement of the affected breast.
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    Avoid massaging the swollen breast to prevent injury and more swelling.
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    Massaging the area may cause an abscess.
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    It is possible to breastfeed exclusively from one breast.

The Academy of Breastfeeding Medicine describes the process of engorgement through to mastitis, abscess, and galactocele, along with a treatment protocol.

Discovering a lump in breasts during breastfeeding

During breastfeeding your breasts will undergo many changes. These changes include your breasts filling with milk and then as your baby feeds the fullness lessens as there is less milk in your breasts. Sometimes lumps appear when your breasts are filling and sometimes these lumps may appear when your breasts are empty.


When your breasts fill with milk, they can become engorged. This can result in lumps throughout the breast, or the entire breast may become uniformly firm. These lumps can also appear in breast tissue in the armpit.

Once your baby starts to feed, the amount of milk in the breast decreases and the breast becomes softer and lumps get smaller and often disappear. Sometimes lumps can remain as some of the milk may be trapped in the milk ducts from the engorgement.

Blocked milk ducts

As the engorgement resolves, some lumps can remain or become noticeable because some milk is trapped in the milk ducts. Just one duct can't become plugged, so it is usually a collection of blocked ducts that produce discomfort. This blockage can persist and if it worsens, it can cause inflammatory mastitis.

Gentle massage is sometimes suggested to try to unblock the duct, but research has shown that this is rarely helpful and can injure the breast tissue and cause more swelling. Anti-inflammatories such as ibuprofen or naproxen can be helpful.


Many years ago, mothers would give up breastfeeding when they got mastitis. But new protocols allow for breastfeeding to continue in many circumstances.

If the blockage does not clear, it can progress to mastitis. Inflammatory mastitis involves the breast tissue that surrounds the blocked ducts and can progress to bacterial mastitis.

The area of inflammation can look pink, and feel warm and painful. Ice, such as a bag of frozen peas can reduce the swelling and relieve some of the discomforts.

Inflammatory mastitis does not usually require antibiotics.

Inflammatory mastitis can progress to bacterial mastitis and the area may become red with increased swelling and pain and may require antibiotics to treat the infection. The antibiotics used in the protocol to treat bacterial mastitis are safe for your breastfeeding baby.

Ice and anti-inflammatories can help to relieve the discomfort.

You should see your primary care provider (PCP) if you have a fever for more than 24 hours.


Bacterial mastitis may progress to an abscess, which is a hard lump, and may require drainage to remove the infectious fluid and reduce discomfort due to the swelling.

Antibiotics may be used, and ice and anti-inflammatories can help with discomfort.


A galactocele happens when a significant amount of milk is trapped, and a cyst develops. If the milk remains trapped, an infected galactocele may result and the cyst may need to be drained.

Antibiotics may be used, and ice and anti-inflammatories can help with discomfort.

Fibrocystic breast disease

Women with fibrocystic breasts may notice some bloody discharge from the nipple during pregnancy and breastfeeding. Usually, there is no reason not to breastfeed even if there is a bloody discharge from the nipple.

Lactating adenoma

A lactating adenoma can develop during pregnancy or breastfeeding. It is a non-cancerous (benign) tumor that completely goes away when you stop breastfeeding.

Anti-inflammatories can help with discomfort.

Reducing discomfort in the affected breast

Often when a duct is blocked, the baby is offered that breast first to reduce the discomfort. This frequently backfires because the breast produces milk in response to the amount of milk that was removed. This is a supply and demand situation, the breast will fill with milk and the discomfort will return. It may be helpful to avoid nursing on the affected breast until the swelling has gone down completely. The baby can feed exclusively on the unaffected side to give the other breast time to become unblocked.

The current protocol recommends offering the other breast so that the affected breast will produce less milk, the swelling will go down and the discomfort can improve. As the swelling goes down, there is a good chance the blocked duct will open up and allow the milk to flow. This can help to prevent the blockage from progressing to mastitis and even an abscess.

Massaging the affected breast is not recommended as this often causes damage to the breast tissue being massaged. The swelling that follows the massage can make things worse and can even create an abscess.

In all cases of concern or if the lump does not go away, a prompt visit to a healthcare practitioner is recommended. Non-painful lumps that come and go are often not a problem.

Lumps can occur anywhere in the breast during breastfeeding. Some can be near the surface and others deep in the breast.

Keep in mind that breast cancer can happen during breastfeeding.

Professional assessment of the breast may be necessary to diagnose and provide appropriate treatment for breast lumps.

When your breasts fill with milk, they can become engorged. This can result in lumps throughout the breast or the entire breast. There are ways to reduce the discomfort, including the use of anti-inflammatories and cold treatment, to avoid the problem progressing further. If in doubt, see your healthcare provider.

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