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Do You Know These 7 Causes of Breast Lumps

June 5, 2024

In this post, let’s look at seven different types of lumps that can develop in your breasts and why they happen.

Image of woman examining for  breast lumps

Here in the UK, breast cancer is the most common type of cancer, with more than 150 women diagnosed every day. (Cancer Research UK)

According to the American Cancer Society, breast cancer was the 2nd most common cancer in 2022.

While breast cancer is significant and not as rare as we would like, there are other causes of lumps that can happen in the breast.

What’s in the Breast?

Regular breast examination is essential once a month and usually after a period for those who are still menstruating.

But when you find a lump – your mind may initially worry about cancer, and you must see your doctor to check out every type of lump. 

So, we will look at types of lumps that can develop in the breast, but before we do that, a quick look at what’s in the breast.

What is inside your breast?

The adult female breast is made of different types of tissue.

A lot of fat. 

Then, you have glandular tissue, which contains cells that can produce or release different products.

Some examples of glands you’ll be familiar with are sweat or salivary glands, thyroid glands, etc. that produce sweat, saliva, or thyroid hormones.

Clearly, from the breasts, you get breast milk.

The glandular tissue in the breast splits into sections called lobes, and these again divide into lobules. 

There is also a network of channels or milk ducts that help transport the milk produced around the breast.

How does this work together?

Milk production happens in the lobules, which connect to the milk ducts that run from the lobes towards the nipple. 

In addition, connective tissue and ligaments support the rest of the breast.

Little-known breast facts

Here are some quick breast factoids:

One of your breasts is usually slightly smaller than the other – that’s normal.

It’s also normal for your breasts to feel a little different at different times of the month, which corresponds to the hormone balance at that time of your cycle.

Just before your period, for instance, your breasts could feel quite lumpy.

Age affects the composition of the breasts.

Younger women have more glandular tissue than fat (because they are more likely to be breastfeeding) than older women. More glandular tissue makes your breasts dense.

For women who’ve been pregnant, you also know the breasts change to become bigger and feel more tender.

By the time a woman gets to menopause and the periods stop, the breast tissue becomes more fatty, which is less dense.

Awareness of the dense appearance of the breast tissue at different ages is helpful – for instance, in mammograms. It is one of the reasons many places only offer mammograms under the age of 40 if you have specific risk factors.

This is because denser breasts, i.e. in younger women, make it more difficult for the mammogram to identify abnormalities.

So now we know what’s in the breast; let’s look at 7 types of breast lumps that can happen.

Breast Cyst

A cyst is a fluid-filled sac that can develop anywhere in the body, including breast tissue.  

They often result from hormonal changes during the menstrual cycle, and we think they happen when the milk glands fill up with fluid.

They are a common cause of a non-cancerous, aka benign, lump in the breast. 

You may get one cyst at a time, but multiple cysts can happen and affect both breasts. They could be small or grow to large sizes. They feel smooth and soft like a grape, but sometimes they feel firm.

Breast cysts can happen at any age, but more often, we see them in women over the age of 35 years, around or before menopause – and sometimes in women after menopause who take HRT. 

They usually do not need treatment unless they grow to large sizes, become painful; if there’s an infection or are causing other problems.

Most cysts will go away by themselves, and once you have a diagnosis with one, there is nothing to worry about.

 Some people have cysts that come and go.

Many times, we cannot tell how long the cyst will last before it goes away.

Fibroadenoma of the Brerast

This is another very common benign or non-cancer condition that causes a smooth lump in the breast. Again, it can develop at any age but more often in younger women and teens. Apart from feeling smooth, it moves around easily under the skin, earning the nickname’ breast mouse’.

Sometimes, just before a period, you might experience pain around the breast from the fibroadenoma. We don’t know precisely what causes fibroadenomas, but the hormone oestrogen may have a role.

 It is formed from tissues or ducts growing over a lobule to create a solid lump.

There are different types of fibroadenoma.

Simple and other types of Fibroadenoma

You may have a simple one when the size is between 1-3 cm (pea size) or a giant fibroadenoma that grows to more than 5 cm. Giant fibroadenomas are more common in pregnancy or breastfeeding.

If the fibroadenoma happens in teenage girls, we call it a juvenile fibroadenoma.

It is multiple fibroadenomas if you have more than one.

Lastly, some women have a complex fibroadenoma that is different from others. The cells of complex fibroadenomas look different to each other when we view them under a microscope.

 Having a fibroadenoma does not usually increase your risk of breast cancer.

However, the complex type may slightly increase the risk of developing breast cancer in future.

After diagnosis with a scan or mammogram, you may also need a biopsy.

This is especially true if you are over 25 years old. A biopsy involves taking small samples of the lump and examining them under the microscope.

Most fibroadenomas do not require treatment.

However, you will be asked to keep an eye on them and return to your GP if they seem to be growing bigger or some other symptom develops.

Surgery may be considered for complex, giant or even juvenile fibroadenomas. This could be under general (excision biopsy) or local anaesthesia (vacuum excision).

Essentially, most fibroadenomas stay the same size.

Some get smaller and eventually disappear with time.

But, some can get bigger – this is more common in teenage girls, during pregnancy, breastfeeding or in a woman taking HRT.

PASH of the Breast

The next cause of a lump in the breast, which is benign, is called PASH.

PASH means pseudoangiomatous stromal hyperplasia. (Stroma means supporting/connective tissue).

It’s a common cause of a painless lump that develops in women commonly before menopause (though it can happen at any age).

It’s also thought to be related to hormone balance issues.

The lump size can vary, and the diagnosis is often clear after the mammogram, scan and biopsy.

PASH doesn’t require treatment; often, you will monitor the lump and return to your doctor if you notice any changes in size or appearance.

Fat Necrosis

Fat necrosis is a benign (non-cancer) condition that causes a lump if an area of fatty breast tissue is damaged. Often, this happens during surgery, radiotherapy to the chest, after a biopsy or following other trauma to the breast or chest, such as a fall or seat belt injury. The injury leads to the death of fatty cells, causing the lump to develop. Trauma could also lead to bleeding or a haematoma forming in the breast. 

If you have fat necrosis, you may feel firm, round lumps in the breast, which some people may find painful or painless.

The skin around the injured area and lump may look thicker, red, darker or bruised. Sometimes, it may even look dimpled, and the nipple pulled in.

 These changes may cause concern that this is breast cancer and why it is important to have all lumps checked by the doctor.

Different tests, including a mammogram, breast scan, biopsy and so on, will help to determine the correct diagnosis.

In the case of fat necrosis, no treatment is usually required. It is harmless, and usually, the body will break it down over time, taking a few months.

However, if the lump gets bigger or you see any other changes to the breasts, please go back to your doctor to look at things again.

Breast Lumps: Lipoma

While we’re on the subject of fat, have you heard of a lipoma?

This is a benign growth of fat cells that can happen anywhere in the body, so it could also develop in the breasts. Breast lipomas are usually small, painless, soft or doughy lumps – but if they press on a nerve, they might cause pain.

 We don’t know what causes them, but they may happen more often after injury to the breast or if you have a family history or conditions associated with developing lipomas.

They are often harmless and do not require treatment.

But if they cause pain or are very large, this can be achieved via surgery or liposuction.


Mastitis is a common cause of a painful lump in the breast that develops following an infection of the milk ducts or tissues around it.

Commonly, we have lactational mastitis, which develops in a woman just after having a baby – whether breastfeeding or not. In this case, the milk ducts are infected. In addition to a lump, you can feel it behind the nipple, the breast can be painful, it can feel hot, and the skin looks red or darker. Some women may have a nipple discharge, and the nipple itself is pulled in (inverted) in some cases. A high temperature also accompanies this state of affairs.

Mastitis could affect anyone else unrelated to pregnancy or breastfeeding. People who smoke are more at risk as the chemicals in the smoke could damage the ducts behind the nipple, making them prone to infection. Smoking can also delay the healing process. 

Having a nipple piercing could also increase the risk of infection.

These are some common causes of breast lumps that are benign, though they can cause considerable distress in some women.

What is a Breast Fibroid

 I’d also like to mention here the so-called ‘Breast Fibroid.’

 Let me know in the comments section if you’ve heard this term before – I’ve been hearing it frequently, and it’s tough to understand what the person using it means.

 First, in medical terminology, there is nothing like breast fibroids.

 Fibroids are benign growths of the womb; the causes are not fully clear, but we know there is an element of hormone imbalance with Progesterone and Oestrogen involved, with other factors like age, genetics, diet, environmental pollutants and so on.

Now, we know that hormone changes can be related to several conditions in the breasts, such as fibroadenoma, cysts, or PASH, which I’ve just been describing. But this doesn’t mean you can have fibroids in the breast.

It is possible to have fibrocystic changes in the breast, which means having fibrous tissue and cysts develop under the influence of hormone changes – it is not the same as fibroids. These are often normal changes that can lead to lumpiness in the breasts. 

SIX – Ductal Carcinoma

Invasive Ductal Carcinoma

So now let’s talk about other causes of breast lumps, and now we are looking at breast cancer or malignancy.

Cancer can develop around or in the milk ducts. There is a non-invasive type that starts in the ducts and does not spread beyond the walls of the duct.

This is ductal carcinoma in situ (DCIS). Another name for this is early ductal cancer.

DCIS can be asymptomatic and often a finding on routine mammograms as part of the breast screening programme. 

However, a small number of people develop symptoms, including:

  • a breast lump 
  • a nipple discharge (that may be blood-stained)
  • a red/scaly rash on the skin around the nipple 

The treatment for DCIS is mainly by surgery to remove an area of the breast or the whole breast. Some women may benefit from hormone therapy as well.

But there is also the invasive ductal carcinoma (IDC). Its other name is invasive breast cancer.

 It is the most common type of breast cancer. It begins in the milk ducts and then spreads through the lining of the ducts into the surrounding breast tissue. 

The symptoms of invasive breast cancer include the typical symptoms we encourage you to monitor:

  • a new lump or thickening in your breast or armpit
  • a change in the size, shape or feel of your breast
  • skin changes in the breast such as puckering, dimpling, a rash or redness of the skin
  • discharge or fluid leaking from the nipple in a woman who isn’t pregnant or breastfeeding
  • changes in the position of the nipple

Treatments include radiotherapy, chemotherapy, hormone therapy, targeted cancer drugs, and others.

Invasive Lobular Breast Cancer

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer. It begins in the breast’s milk-producing glands (lobules) and can spread to surrounding tissues.

It may not develop into a lump in all cases – many women would instead describe a thickening in the breast with ILC. 

Other possible symptoms include:

  • the nipple may turn inward
  • there may be skin changes like dimpling or thickening

While invasive lobular breast cancer can cause these particular symptoms, it’s also worth being aware of the general symptoms of breast cancer.

There are other types of breast cancer, for example, Triple-negative breast cancers (whose cells don’t have receptors for the hormones oestrogen and progesterone and a protein called Human Epidermal Growth Factor Receptor 2 (HER2)), and other less common types of cancer which could also cause breast changes including a lump.

Hopefully, this post gives a good overview of some causes of breast lumps and motivates you to check your breasts regularly and seek medical advice if you notice a lump or any changes in the breasts so they can be checked out. 

You can see both benign and malignant conditions can present with a lump.

Check out DrTasha, on YouTube, who shares information about breast cancer.

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Editing by AskAwayHealth Team


All AskAwayHealth articles are written by practising Medical Practitioners on a wide range of healthcare conditions to provide evidence-based guidance and to help promote quality healthcare. 

The advice in our material is not meant to replace the management of your specific condition by a qualified healthcare practitioner.
To discuss your condition, don’t hesitate to get in touch with a health practitioner or reach us directly.

Image Credits: Canva

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