What Is Breast Cancer?

  • 1st Revision: Stanley Anthony Chidera [Linkedin]


Breast cancer affects millions of women worldwide. It’s also concerning that the only explanation for about half of its cases is gender (female) and age (above 40).1 But before we go any further, we have to answer the question, what is breast cancer?

Breast cancer is the uncontrolled growth of abnormal cells in the breast that eventually forms a tumour that may spread to the rest of the body. It usually starts in the ducts or lobules, but it can also develop in the nipple, connective tissue, and blood and lymph vessels of the breast (American Cancer Society - Breast Cancer)2, (Cancer Research UK - Breast Cancer)3.1

Now that we know what breast cancer is, let’s unpack the rest. This article covers everything from its risk factors and treatment to diagnosis and prevention. So, stick around to find out more. 

Causes of breast cancer

There’s no definite cause for each case of breast cancer. But many risk factors compromise breast health and increase your chances of getting breast cancer.2,3

A. Risk factors outside patients’ control:

  • Age: Breast cancer risk increases with age. Most breast cancers are seen in women aged 55 and older
  • Gender: Breast cancer is most common in women, but men can get it too (rare cases)
  • Blood group: Women with A+ blood have an increased risk of breast cancer compared to women with AB- blood
  • Family and personal history of breast cancer: Having 1 or 2 first-degree relatives with breast cancer and cancer in one breast increases breast cancer risk
  • Inherited gene mutations: These mutations account for only 10% of breast cancers. The remaining 90% develop from acquired genetic changes throughout a person’s life
  • Race and ethnicity: Asian, Hispanic, and Native American women have lower rates of developing and dying from breast cancer than African American and white women
  • Height: Although the reasons are unclear, taller women have a higher breast cancer risk than shorter women
  • Dense breasts: Women with dense breast tissue have a higher breast cancer risk than those with average density
  • Benign breast conditions: Benign breast disorders that result in the growth of abnormal cells increase breast cancer risk
  • Early menstruation and late menopause: Menarche before age 12 and menopause after age 55 are associated with increased breast cancer risk
  • Radiation exposure: Cancer patients who underwent radiation therapy to the chest when they were young adults or teens have an increased risk of breast cancer2,3,4

B. Lifestyle-related risk factors:

  • Alcohol consumption: Having 2-3 drinks daily increases breast cancer risk by 20% in women
  • Overweight and obesity: High-fat tissue content after menopause raises estrogen levels and increases breast cancer risk
  • Physical activity: The American Cancer Society recommends moderate (150-300 minutes) or vigorous (75-150 minutes) (or a combination of both) physical activity every week to reduce breast cancer risk
  • Breastfeeding and pregnancy: Having many children and breastfeeding when young lowers breast cancer risk. But pregnancies later in life increase it
  • Hormonal therapy: Oral contraceptives and birth control pills or implants slightly increases breast cancer risk. While prolonged post-menopausal hormone therapy dramatically increases it
  • Breast implants: They’ve been linked to rare cancer types including BIA-ALCL, lymphomas, and squamous cell carcinomas
  • Air pollution: High levels of it are associated with increased post-menopausal breast cancer in women
  • Sleep duration: Insomnia and getting less sleep increase breast cancer risk
  • Diabetes: It increases breast cancer risk in post-menopausal and overweight women by 20%2,3,4

C. Unclear risk factors:

  • Smoking: Prolonged heavy smoking slightly increases breast cancer risk. But it’s unclear if passive smoking does as well
  • Diet: Healthy diets may lower breast cancer risk and low-fat diets reduce your chances of dying from it
  • Night shift work: Breast cancer research shows that prolonged overnight work moderately increases breast cancer risk2,3,4

Signs and symptoms of breast cancer

Besides an irregular breast lump or thickening, the other breast cancer symptoms include: 

  • Changes in the shape, size, texture, and swelling of the breast
  • Breast and nipple pain
  • Breast skin changes like puckering, dimpling, rashes, redness, and flakiness
  • Nipple discharge in women who aren’t pregnant or breastfeeding
  • Changes in nipple position.
  • Swollen lymph nodes or lumps under the arm or near the collarbone.

Not all symptoms indicate breast cancer. Lumps could also indicate benign breast conditions. That’s why watching out for breast cancer symptoms does not take precedence over breast cancer screening since these tests can detect it before symptoms can appear.2,3

Management and treatment for breast cancer

The type of breast cancer treatment used depends on the cancer stage, tumour location and size, and the patient’s health.3The treatments are either standard (in use) or experimental (undergoing clinical trials) (National Cancer Institute - Breast Cancer)5. The ones currently in use are:

A. Local treatments:

  • Surgery – It’s used to remove breast cancer and limit its spread. The type of surgery performed depends on the cancer stage and the patient’s health or choice.
  1. Breast-conserving surgery – It’s a surgery that removes a part of the breast containing cancer and normal tissue around it. 
  1. Mastectomy – It’s a surgery that removes the entire breast and nearby breast tissue. 
  1. Breast reconstruction surgery – It’s a surgery that restores the shape of breasts after a mastectomy. 
  1. Lymph node removal – It’s a procedure to check and limit the spread of breast cancer by removing a few lymph nodes under the arm. 
  • Radiation therapy: It’s a treatment that uses high-energy rays to destroy cancer cells by disrupting their DNA. Various types of external beam radiation therapy (EBRT) are routinely used.2,6

B. Systemic treatments:

  • Chemotherapy 
  • It uses drugs that inhibit the growth the cancer cells. They are administered orally or intravenously and in cycles to allow for recovery from the side effects. 
  • The choice of drugs depends on the cancer stage and when it’s given (neoadjuvant or adjuvant chemotherapy). 
  • Hormone therapy/ Endocrine therapy 
  • It uses medicines that block the attachment of hormones (estrogen and progesterone) to the receptors of cancer cells dependent on them for their growth.  
  • The medicines in hormone therapy used are Selective estrogen receptor modulators (SERMs), selective estrogen receptor degraders (SERDs), aromatase inhibitors (AIs), and luteinizing hormone-releasing hormone (LHRH) agonists. 
  • Targeted drug therapy – It uses medicines administered orally or intravenously to target specific proteins needed for breast cancer cell growth.
  1. Gene therapy – It uses molecular modification techniques to correct mutated genes that aid in breast cancer progression. 
  1. Anti-angiogenesis drugs – These medicines cut off cancer cells’ blood supply, thus halting their development and killing them.
  • Immunotherapy – It stimulates the immune system to recognise and destroy cancer cells by acting on certain proteins that trigger an immune response.
  1. Human monoclonal antibodies – They attach themselves to proteins of breast cancer cells (HER2), thereby stopping their growth.  
  1. Cancer vaccines – It uses cancer cells to excite the immune system to attack and destroy them.2,6

Breast cancer treatments are often used concomitantly depending on the severity of the cancer.2,3,5,6 Breast cancer care also includes maintaining physical and mental health through coping strategies and prehabilitation programmes.3


How is breast cancer diagnosed

Breast cancer is diagnosed by tests examining the breasts and breast tissue samples. These tests are:

  • Physical examination/Clinical breast exam (CBE)

Clinicians examine the breasts, area around the neck, collarbone, armpits, and lymph nodes for breast cancer symptoms. It’s usually offered for high-risk patients. 

  • Self–examination/ Breast self-exam (BSE)

Women examine their breasts for changes in their shape and feel. 

  • Mammography 

Mammograms are low-dose X-rays of the breast routinely used in breast screening. But It’s less likely to find breast cancers in women with dense breasts.

  • Breast Ultrasound

It’s a breast imaging test using sound waves that can detect tumours in women with dense breast tissue, identify a tumour’s size and location, and guide a biopsy. 

  • Breast MRI

It’s a breast imaging test using radio waves and a magnetic field. It provides more accurate results with no radiation exposure. It’s used with mammograms.

  • Breast biopsy

Clinicians extract a sample of suspected cancerous breast tissue to check for breast cancer cells. They’re usually done with CBEs and breast imaging tests.2,5,6

Sometimes, CT, PET, or bone scans are done to check if breast cancer has spread to the rest of the body. The type of cancer is determined by performing hormone receptors, cancer proteins, and tumour profiling tests on the breast cells.2,3

Can I prevent breast cancer

There’s no foolproof method to prevent breast cancer. However, you can lower your risk of developing it by limiting risk factors within your control. Women at high risk must take extra measures to lower their breast cancer risk.2

Steps for all women

  • Maintain a healthy weight by balancing your dietary intake and physical activity.
  • Stay active by exercising, playing a sport, doing household chores, or having a physically active job.
  • Adopt a healthy diet rich in vegetables, fruits, and calcium-rich dairy and low in red and processed meats, and fat.
  • Avoid or limit alcohol to not more than 1 drink a day.2,3

Steps for women at risk

Women are at risk when they have a strong family history of breast cancer or ovarian cancer, have inherited gene mutations (BRCA1 and BRCA2), or have DCIS or LCIS.

  • Genetic counselling and testing: Genetic counsellors review family histories and recommend genetic tests for women with a suspected inherited genetic mutation
  • Medications: Taking selective estrogen receptor modulators (SERMs) and aromatase inhibitors lowers breast cancer risk. However, they have side effects
  • Preventive surgery: Prophylactic mastectomy or oophorectomy is only recommended for high-risk women. They only lower breast cancer risk but do not eliminate it
  • Breast screening: Frequent doctor visits (every 6-12 months, mammograms and MRIs for healthy, high-risk women in their 30s detect breast cancer early, but do not lower its risk2,3

What are the breast cancer stages

Breast cancer stages indicate cancer size and how far it has spread. In the UK, the most commonly used systems to stage breast cancer are the TNM (Tumour, Node, Metastasis) and the number staging system.3

The TNM staging system divides breast cancers based on:

  • Tumour size (denoted by T)
  • The extent of spread to lymph nodes (denoted by N)
  • The extent of spread to the rest of the body (denoted by M)3

The number staging system divides breast cancer into 4 stages:

  • Stage 0:

Pre-invasive breast cancer is restricted to the breast ducts and yet to spread to the surrounding breast tissue.

  • Stage 1:

Early-stage breast cancer that’s small and restricted to the breast tissue or lymph nodes near the breast. 

  • Stage 2:

Early-stage breast cancer in either the breast, bordering lymph nodes in the armpits and breastbone or both. 

  • Stage 3:

Locally advanced breast cancer that has spread from the breast and lymph nodes to the skin of the breast or the chest wall but not to the rest of the body. 

  • Stage 4:

Advanced or secondary breast cancer (metastatic breast cancer) that has spread to other organs like the lungs, liver, brain, or bones.3,6

How common is breast cancer

According to WHO, breast cancer is the world’s most prevalent cancer. It can occur in any woman at any age post-puberty, with increasing prevalence as they get older.1

In the UK, breast cancer accounts for 15% of new cancer cases and 55,000 women are diagnosed with it yearly. Although rare (1% of breast cases), men also develop breast cancer.3

What are the types of breast cancer

There are many types of breast cancer. But it is mainly divided into invasive and non-invasive breast cancers.

  • Non-invasive breast cancers do not spread from the lobules or the ducts to the surrounding breast tissues. Examples: Ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS)
  • Invasive breast cancer spreads to the nearby breast tissues and the rest of the body via the blood or lymph system. Examples: Invasive ductal carcinoma and invasive lobular carcinoma2,6

Most breast cancers develop in the cells of the ducts or lobules and 70-80% of them are invasive ductal carcinomas.2,3

Special breast cancer types have cancer cells with unique features that affect their treatment and outlook. Although rare, they’re more severe than other cancer types.

  • Triple-negative breast cancer (15% of cases): The cancer cells lack receptors for estrogen, progesterone, and HER2, thus making it difficult to treat
  • Inflammatory breast cancer (1-5% of cases): The cancer cells cause skin inflammation of the breast by blocking the lymph channels/ ducts

Rare breast cancer types develop in other areas of the breast. 

  • Paget’s disease (1-3% of cases): It develops in the nipple and the areolar (the dark-round area of the nipple) resulting in discharge, bleeding, and skin inflammation. It’s usually invasive(can spread to other body structures)
  • Angiosarcoma (1% of cases): It’s invasive and originates in the cells of the circulatory system (blood and lymph vessels), spreading to the nearby breast tissues or skin.2,3,6 

When should I see a doctor

You should consult a doctor if you observe any breast cancer symptoms. Women should know how their breasts usually look and feel and report any changes, especially if they’re at high risk.2,3,5,6


Breast cancer develops in various parts of the breast. It’s prevalent in women but can occur in men on rare occasions. While it has no definitive cause, many risk factors outside or within a patient’s control increase its risk. That’s why early diagnosis through breast screening tests is the best way to ensure effective and prompt treatment. You can prevent breast cancer by being physically active and eating healthy. But high-risk patients should take extra measures to lessen their chances of developing it. 


  1. Breast cancer [Internet]. [cited 2023 Feb 20]. Available from: https://www.who.int/news-room/fact-sheets/detail/breast-cancer
  2. Breast cancer | breast cancer information & overview [Internet]. [cited 2023 Feb 20]. Available from: https://www.cancer.org/cancer/breast-cancer.html
  3. Breast cancer [Internet]. [cited 2023 Feb 20]. Available from: https://www.cancerresearchuk.org/about-cancer/breast-cancer
  4. Momenimovahed Z, Salehiniya H. Epidemiological characteristics of and risk factors for breast cancer in the world. Breast Cancer: Targets and Therapy [Internet]. 2019 Apr 10 [cited 2023 Feb 20]:151-64. Available from: Epidemiological characteristics of and risk factors for breast cancer in the world
  5. Breast cancer screening (Pdq®)–patient version - nci [Internet]. 2022 [cited 2023 Feb 20]. Available from: https://www.cancer.gov/types/breast/patient/breast-screening-pdq
  6. Akram M, Iqbal M, Daniyal M, Khan AU. Awareness and current knowledge of breast cancer. Biol Res [Internet]. 2017 Dec [cited 2023 Feb 20];50(1):33. Available from: http://biolres.biomedcentral.com/articles/10.1186/s40659-017-0140-9
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Malaika Solomon

Bachelor of Pharmacy - B Pharm, JSS Academy of Higher Education and Research, India.

I'm an experienced content writer currently pursuing a post graduate diploma in Clinical Research.
I'm passionate about writing articles that bring accurate and digestible information about healthcare and medical research.

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