Causes of male breast cancer

By Dr Ananya Mandal, MD

Normal cells have a tightly regulated system that guides when they would grow, reproduce and eventually die. Cancer occurs in normal cells when this regulation fails and cells grow uncontrollably. There are defects in the coding information in cells, which is present in the deoxyribonucleic acid (DNA) that is found in the nucleus of cells in all human cells.

A change in the code is called a mutation and can alter the instructions that control cell growth leading to cancer. These deranged cells grow in an uncontrollable manner and produce a lump of tissue that is known as a tumor.

Once the cancer is formed it can quickly grow and spread to other parts of the body. Breast cancer may spread directly into the surrounding muscle and skin and may also spread via blood or lymphatic system to different organs of the body like the lungs, brain and liver. The spread first occurs to the nearby lymph nodes that may appear swollen.

Breast cancer is rare among men compared to its incidence in women. There are several risk factors that raise the chance of men getting breast cancer. These include increasing age, inheritance, exposure to female hormone estrogen and so forth.

Increasing age and risk of male breast cancer

Increasing age is the common risk factor. Most cases occur after 60 to 70 years of age.

Genetics and inherited breast cancer

A genetic mutation may be inherited from family members. Those with a family member (both male or female) have a higher risk of breast cancer. The most significant mutation identified to date is known as the BRAC2 mutation.

One study that was carried out in the UK found that 1 in 20 men with breast cancer have the BRAC2 mutation. In addition at least 1 in 5 men who develop breast cancer, have a first-degree relative (a parent or a sibling) who also has a history of breast cancer.

Exposure to female hormone estrogen

Long term exposure to estrogen can increase the risks of breast cancer in men. Normally men have a low level of this hormone but levels may rise in certain conditions in men like:

  • those undergoing hormonal therapy (those with prostate cancer and transsexuals who are undergoing a male to female sex change)
  • obese men
  • a genetic condition called Klinefelter's syndrome

Klinefelter's syndrome is a major risk factor for breast cancer in men. Men who have the condition are 20 times more likely to develop breast cancer than the male population at large.

Boys with Klinefelter's syndrome are born with much higher levels of oestrogen than normal. They have an extra X chromosome (XXY) compared to normal males who have XY chromosomes. It is estimated that 1 in every 1,000 people are affected by Klinefelter's syndrome.
Exposure to environmental factors

Men who work in hot environments are twice as likely to develop breast cancer compared with men who work in cooler environments. In includes blast furnace workers, steel workers, those working at car manufacturing plants and steel works. It is speculated that excess heat may damage the testicles causing a decline in male hormones and rise in female hormones like estrogen.

In addition, exposure to certain chemicals may increase the risk of developing breast cancer in men. Those men working with perfumes and soaps are seven times more likely to develop breast cancer than the male population at large. Those exposed to Polycyclic aromatic hydrocarbons (as in petrol and exhaust fumes) are also at a raised risk.

Exposure to radiation

Men who have been exposed to radiation of the chest are at a higher risk.

Chronic liver disease

Chronic liver disease also leads to high levels of female hormones estrogen and increases the risk of male breast cancer. This is seen in men with chronic alcoholism.

Pituitary tumors

Those with pituitary tumors or Pituitary adenomas leading to increased levels of the hormone prolactin in blood are at a higher risk of developing breast cancer in both breasts.

Gynecomastia

Gynecomastia or enlargement of male breasts is not a risk factor for male breast cancer.

Reviewed by April Cashin-Garbutt, BA Hons (Cantab)

Sources

  1. http://www.nhs.uk/Conditions/Cancer-of-the-breast-male/Pages/Causes.aspx
  2. http://www.bbc.co.uk/health/physical_health/conditions/male_breast_cancer.shtml
  3. http://www.patient.co.uk/doctor/Male-Breast-Cancer.htm
  4. http://ww5.komen.org/uploadedfiles/content_binaries/806-320a.pdf
  5. http://www.cancer.org/acs/groups/cid/documents/webcontent/003091-pdf.pdf
  6. http://envirocancer.cornell.edu/factsheet/general/fs43.bcMale.pdf

Further Reading

Last Updated: Nov 8, 2012

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