What is breast cancer?

Breast cancer is a disease in which abnormal cells grow in the breast, forming tumours. It is the most common type of cancer diagnosed in people assigned female at birth (AFAB) and the leading cause of cancer-related deaths among people AFAB globally.¹ While breast cancer can also occur in people assigned male at birth (AMAB), it is 100 times more common in people AFAB.² Every year, around 55,400 people are diagnosed with breast cancer in the UK. 

Breast cancer cells originate in the breast lobules (the glands that produce milk) and ducts (which carry the milk to the nipple). In their early form, they are not life-threatening and are referred to as non-invasive or ‘in-situ’ breast cancer. However, as the cancer cells spread and migrate into the nearby breast tissue, they form tumours, and this is called invasive breast cancer. 

Non-invasive (in-situ) breast cancer

This is referred to as stage 0 breast cancer, which has not yet spread beyond the area where it first developed. The most common form of non-invasive breast cancer is ductal carcinoma in situ (DCIS), and this is confined to the breast’s ducts.³ Another less common form is lobular carcinoma in situ (LCIS), which involves a sudden increase in the number of cells within the milk glands (lobules). This type of non-invasive cancer is considered a marker for the risk of invasive breast cancer, as someone with this diagnosis can be up to nine to ten times more likely to develop invasive breast cancer.⁴

Invasive breast cancer

This type of breast cancer is referred to as ‘invasive’ because the cancer cells in the lobules and ducts break through the walls to invade surrounding breast tissue. This is different from metastatic breast cancer, which occurs when the cells spread to other organs or lymph nodes, also known as secondary breast cancer. 

Invasive lobular carcinoma (ILC) accounts for 5%-15% of invasive breast cancers.⁵ This form of cancer often spreads (metastasizes) to other body areas. Biologically, it is a distinctly different disease from the more common type of invasive breast cancer: infiltrating (or ‘invasive’) ductal carcinoma (IDC). This is more commonly known as ‘invasive breast cancer’. Most cases are classified as NST (no specific type) or NOS (not otherwise specified), meaning that cancer cells do not have the specific microscopic features that rarer types of cells may have. IDC accounts for around 80% of breast cancer diagnoses.⁵

There are other, rarer types of breast cancer, including:

• Medullary breast cancer
• Mucinous breast cancer
• Tubular breast cancer
• Inflammatory breast cancer
• Paget’s disease of the nipple
• Phyllodes tumours

What are the symptoms of breast cancer?

Symptoms of breast cancer in people assigned female at birth (AFAB)

Common symptoms of breast cancer in people AFAB can include:

• Changes in the skin of the breast, such as redness or dimpling 
• A change in the size and/or shape of the breast(s)
• A lump or swelling of the breast, chest, or armpit
• Nipple discharge (if you are not pregnant/breastfeeding) which may contain blood 
• Pain in the breast or armpit area which doesn’t go away 
• Changes to the nipple including a rash, change in shape/look, or it turning inwards 

Symptoms of breast cancer in people assigned male at birth (AMAB) 

Common symptoms of breast cancer in people AMAB can include:

• A lump or swelling in the chest or armpit area 
• Nipple discharge which may contain blood 
• A change in the size or shape of either side of the chest 
• Changes to the nipple including a rash, change in shape/look, or it turning inwards 
• Chest sores or ulcers 

Symptoms of secondary breast cancer

If breast cancer has spread to other parts of the body, it is called secondary breast cancer. The symptoms of this can depend on which body parts the cancer has spread to - this most often affects the bones, liver, lungs, or brain. You might also experience generalised symptoms such as: 

• Trouble sleeping (insomnia)
• Nausea or vomiting 
• Feeling unwell with no obvious reason 
• Losing weight without trying or loss of appetite 
• Lack of energy and fatigue 

What are the risk factors for breast cancer?

Some risk factors for breast cancer include:

Age

Apart from sex (with people AFAB being far more at risk than people AMAB), ageing is one of the most significant risk factors for breast cancer. In general, breast cancer occurs more frequently in older people and most cases occur in people AFAB over 50 years old.

Alcohol

Moderate alcohol consumption has been linked to an increased risk of breast cancer of around 30-50%.⁶ Each unit of alcohol increases your risk of breast cancer, so it is recommended to cut back or, if possible, entirely cut out your alcohol consumption. 

Early menarche and late menopause

Research has shown that for every year menarche (a woman’s first period) is delayed, your risk of breast cancer can be reduced by 10-20%.⁷ Likewise, for every 5-year difference in the age at menopause, your breast cancer risk can change by about 17%, with later menopause associated with a higher risk of breast cancer.⁸

First pregnancy 

It is thought that your first pregnancy causes changes to your breast tissue which makes it more immune to cancer. It is therefore estimated that a woman who has her first child at 18 years old has only one-third the breast cancer risk of a woman who has her first child at 35 years old or later.⁹

Breastfeeding

Breastfeeding lowers your risk of developing breast cancer, and the longer you breastfeed, the more your risk is reduced. 

Family history 

Almost 25% of all breast cancer cases are related to family history. A UK study showed that women with one first-degree relative with breast cancer have a 1.75x higher risk of also developing it.¹¹

HRT and the contraceptive pill

HRT (hormone replacement therapy) and the contraceptive pill can both increase your risk of developing breast cancer, but only slightly. 

Being overweight

Being overweight or obese after menopause can increase your breast cancer risk as a person AFAB. Being overweight is also a risk factor for people AMAB for developing breast cancer. 

How is breast cancer diagnosed?

In the UK, people AFAB aged between 50 and 70 years (and some trans or non-binary people) will undergo breast screenings. These are highly beneficial because they can detect cancers early, making them easier to treat. 

If something is picked up on your screening, or if you have symptoms, your GP may refer you for tests such as: 

• A mammogram - an x-ray of your breasts
• A breast ultrasound scan - produces high-frequency sound waves to create a picture of the inside of your breast

The results of these tests will help your doctor decide if you need to have a breast biopsy, in which a sample of your breast tissue will be taken and sent to a lab. This will allow them to assess whether you have breast cancer, and if so, identify its type. 

If the biopsy shows that you do have breast cancer, you may undergo more tests to stage the cancer. 

What are the treatment options for breast cancer?

Treatment for breast cancer can depend on the size and type of cancer, its location, whether it has spread, and your general health. If you are diagnosed with breast cancer, you will work with a specialist team to determine the most suitable treatment for you and to discuss the benefits and potential side effects of the treatment options available. 

The main treatment option is usually surgery, which could involve removing the part of the cancerous part of the breast, the lymph nodes (glands) in your armpit, or, in some cases, the entire breast (a mastectomy).

Other treatment options include: 

• Radiotherapy
• Chemotherapy
• Hormone therapy
• Targeted medicines and immunotherapy

Secondary breast cancer generally cannot be cured. If diagnosed with secondary breast cancer, you will be offered treatments aimed at managing your symptoms and slowing the spread of cancer. Many people with a diagnosis of secondary breast cancer can live a normal life for several years.

What is the prognosis for breast cancer?

Generally, survival rates for breast cancer are good, especially if you receive an early diagnosis. Survival can depend on the type and stage of your cancer, your general fitness and previous treatment.

According to Cancer Research UK, generally for people AFAB with breast cancer in England:

• Around 95% will survive their cancer for 1 year or more after diagnosis
• Around 85% will survive their cancer for 5 years or more after diagnosis
• Around 75% will survive their cancer for 10 years or more after diagnosis

Your doctor can discuss the specifics of your prognosis with you. 

How can breast cancer be prevented?

Breast cancer cannot always be prevented, but going for breast screenings when you are invited will help to detect any cancer early. The NHS also recommends doing the following to lower your breast cancer risk: 

• Avoid consuming more than 14 units of alcohol per week
• Try to lose weight if you are overweight 
• Try to quit smoking 
• Talk to your GP if you have concerns about the effect of HRT or the contraceptive pill on your risk of breast cancer 
• Talk to your GP about genetic testing if breast or ovarian cancer runs in your family 

What support resources are available for breast cancer patients?

When dealing with a cancer diagnosis, support is vital. There are lots of organisations, support groups, and other resources out there to help you cope if you are diagnosed with breast cancer. You can find them here. 

You can also reach out to Cancer Research UK’s free nurse helpline at 0808 800 4040 (Mon-Fri, 9 a.m.-5 p.m.) if you have any questions or concerns. Alternatively, you can send them a question online or join their dedicated cancer forum for support. 

Summary

Breast cancer occurs when abnormal cells in the breast grow into tumours. It's the most common cancer in people assigned female at birth (AFAB) but can also affect people assigned male at birth (AMAB). Early symptoms include lumps, changes in breast shape or size, and unusual nipple discharge. Risk factors include age, family history, alcohol use, and being overweight. Early detection through screenings like mammograms improves survival rates, and treatments include surgery, radiotherapy, and chemotherapy. Adopting a healthy lifestyle and attending regular screenings can help reduce the risk of breast cancer.