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A risk factor is anything that affects your chance of gettinga
disease such as cancer. Different cancers have different risk
factors. For example, exposing skin to strong sunlight is a risk factor
for skin cancer. Smoking is a risk factor for cancers of the lung,
mouth, larynx (voice box), bladder, kidney, and several other organs.
But risk factors don't tell us everything. Having a risk
factor, or even several, does not mean that you will get the disease.
Some men with one or more breast cancer risk factors never develop the
disease, while most men with breast cancer have no apparent risk
factors. Even when someone has a risk factor, there is no way to prove
that it actually caused the cancer.
We don't yet completely understand the causes of breast cancer
in men, but researchers have found several factors that may increase
the risk of getting it. As with female breast cancer, many of these
factors are related to sex hormone levels in the body.
Aging
Aging is an important risk factor for the development of
breast cancer in men. Men with breast cancer are on average about 67
years old when they are diagnosed.
Family history of breast cancer
Breast cancer risk is increased if other members of the family
("blood relatives") have had breast cancer. About 1 out of 5 men with
breast cancer have close male or female relatives with the disease.
Inherited gene mutations
A mutation (change) in the BRCA2 gene, which is responsible
for some breast cancers in women, probably accounts for about 1 in 10
breast cancers in men. BRCA1 mutations can also cause breast cancer
in men, but they seem to be responsible for fewer cases than mutations
in the BRCA2 gene. People with these mutations typically have a strong
family history of breast cancer, when they are younger age
(under 60).
Other mutations that may be responsible for some breast
cancers in men include those in genes called CHEK2 and PTEN.
Klinefelter syndrome
This is a congenital condition (present at birth) that affects about
1 in 1,000 men. Normally the cells in men's bodies have a single X
chromosome along with a Y chromosome, while women's cells have 2 X
chromosomes. Men with this condition have cells with more than 1 X
chromosome (sometimes as many as 4). This causes their testicles to be
smaller than usual and they may not produce functioning sperm cells,
making them infertile. Compared with other men, they have lower levels
of androgens (male hormones) and more estrogens (female hormones). For
this reason, they often develop gynecomastia (benign male breast
growth).
Some studies have found that men with Klinefelter
syndrome are more likely to get breast cancer than other men. One study
of men with this syndrome found that the risk of getting breast cancer
was about 1%. But this is a hard area to study because these are both
uncommon problems, and it is hard to collect enough cases to be sure.
The risk seems to be increased, but overall it is still low because
this is such an uncommon cancer, even for men with Klinefelter
syndrome.
Radiation exposure
A man whose chest area has been treated with radiation (usually
for treatment of a cancer inside the chest, such as lymphoma) has an
increased risk of developing breast cancer.
Alcohol
Heavy drinking (of alcoholic beverages) increases the risk of
breast cancer in
men. This may be because of its effects on the liver (see next
paragraph).
Liver disease
The liver plays an important role in sex hormone metabolism by
making binding proteins that carry the hormones in the blood. These
binding proteins affect the hormones' activity. Men with severe liver
disease such as cirrhosis have relatively low levels of androgens and
higher estrogen levels. Therefore, they may have an increased risk of
developing breast cancer.
Estrogen treatment
Estrogen-related drugs are sometimes used in hormonal therapy
for men with prostate cancer. This treatment may slightly increase
their breast cancer risk. However, this risk is small compared with the
benefits of this treatment in slowing the growth of prostate cancer.
Men taking high doses of estrogens as part of a sex change
procedure may also have a higher breast cancer risk.
Obesity
Recent studies have shown that women's breast cancer risk is
increased by obesity (being extremely overweight) during her adult
life.
Obesity is probably a risk factor for male breast cancer as well. The
reason is that fat cells in the body convert male hormones (androgens)
into female hormones (estrogens). This means that obese men have higher
levels of estrogens in their body. Some obese men may notice that they
don't have to shave as frequently as other men. They might also have
trouble fathering children. Regular exercise and maintaining a healthy
weight may help reduce the risk of breast cancer, as well as that of
many other diseases and cancers.
Conditions affecting the testicles
Some studies have suggested that certain conditions that
affect the testicles, such as having an undescended testicle, having
mumps as an adult, or having one or both testicles surgically removed
(orchiectomy) may increase breast cancer risk. More research is needed
in this area.
Certain occupations
Some reports have suggested an increased risk in men who work
in hot environments such as steel mills. This could be because
long-term exposure to higher temperature can affect the testicles,
which in turn would affect hormone levels. Men heavily exposed to
gasoline fumes may also have a higher risk. Further research is needed
to confirm these findings.
Last Medical Review: 01/14/2010
Last Revised: 01/14/2010
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