Breast cancer (male) - Causes of breast cancer in men

It's not clear exactly what causes breast cancer in men, although several things that can increase your risk of developing the condition have been identified.

About cancer

The body is made up of millions of different cells. Cancer happens when cells multiply in an abnormal way. When cancer affects organs and solid tissues, it causes a growth called a tumour to form. Cancer can occur in any part of the body where cells multiply abnormally.

In breast cancer, cells in the breast tissue are affected.

Left untreated, cancer can quickly grow and spread from the breast into nearby tissue or other parts of the body. This usually happens through the lymphatic system, but can also spread through the bloodstream.

The lymphatic system is a series of glands located throughout the body and linked together in a similar way to the blood circulation system.

Once the cancer reaches your lymphatic system, it can spread to any other part of your body, including your bones, blood and organs.

Increased risk

A number of things that can increase your risk of breast cancer developing have been identified.

Age

Like many cancers, men have an increased risk of developing breast cancer as they get older. Most cases are diagnosed in men aged 60-70. It's  rare for young men to develop the condition.

Genetics and family history

A genetic mutation is where instructions carried in all living cells become scrambled in some way which means one or more of the body’s processes do not work in the way they should.

There are a number of genetic mutations known to increase your risk of developing breast cancer. The most significant mutation identified is known as the BRAC2 mutation. One study carried out in the UK found one in 20 men with breast cancer have the BRAC2 mutation.

There is also evidence that breast cancer can run in families, as one in five men who develop breast cancer have a first-degree relative, such as a mother or sister, who has developed breast cancer.

Routine testing for the faulty genes that cause breast cancer in men is not usually carried out on the NHS. However, some private clinics offer gene testing. Tests can be expensive with prices ranging from around £2,000 to £3,000.

Oestrogen

There is evidence that high levels of the hormone oestrogen, or prolonged exposure to it, can increase the risks of breast cancer in men.

Compared to women, men tend to have low levels of oestrogen, but there are circumstances that can increase the levels of oestrogen in men. These include:

• hormone treatments – man-made (synthetic) versions of oestrogen are often used to treat prostate cancer and are also given to transsexuals undergoing a male to female sex change
• obesity – obese men have higher levels of oestrogen than normal
• cirrhosis – long-term scarring of the liver often caused by long-term alcohol misuse

There is also a rare genetic condition affecting males called Klinefelter's syndrome. This is a congenital condition (boys are born with it) and it means affected males produce less of the hormone testosterone than usual.

As testosterone usually helps to limit the effect of oestrogen, men with Klinefelter's syndrome are more likely to develop breast cancer than the general male population.

Occupational risks

There is evidence that men who work in hot environments are twice as likely to develop breast cancer compared with men who work in cooler environments. Environments linked to an increased risk of breast cancer in men include:

• blast furnaces
• steel works
• rolling mills – a factory where metal (usually steel) is shaped using rollers
• car manufacturing plants

One hypothesis to help explain the link between working environment and the increased risk of developing breast cancer is that excessive heat may damage the testicles, which could lead to an increase in oestrogen levels.

Another hypothesis is that working in hot environments usually involves exposure to certain chemicals which may increase the risk of developing breast cancer in men.

Rates of breast cancer are also unusually high in men who manufacture perfumes and soaps. They are seven times more likely to develop breast cancer than the male population at large. The reason for this increased risk is still unclear. Exposure to certain chemicals seems to be an obvious possibility, but this has not yet been proven.

Radiation

Exposure to radiation has been linked to an increased risk of developing breast cancer in men.

Research has found that men who received a course of radiotherapy (where high energy X-rays are used to kill cancerous cells) directed at the upper chest were seven times more likely to develop male breast cancer compared to the population at large.

However, even a seven-fold increase means the chance of developing breast cancer is still very low.