Breast cancer affects men as well as women, but it is about 100 times less common in men. The American Cancer Society estimates that 1,910 new cases of invasive male breast cancer will be diagnosed in the United States in 2009. Men who develop breast cancer often do so later in life, around the age of 70.
A man’s chance of surviving breast cancer is similar to that of a woman diagnosed at the same stage of disease. Male breast cancer is more likely to be cured if it is discovered early. But because many men do not realize that they can develop the disease they don’t seek medical attention when they first discover an abnormality. Therefore, breast cancer is generally diagnosed at later stages in men than in women.
Male and female breast cancers differ in some aspects, but have many features in common. Because the male form of the disease is so rare, conducting clinical research is a challenge. However, much of the research done in women with breast cancer has led to advances in the treatment of male breast cancer.
The Female and Male Breast
Early in life, boys and girls have a similar amount of breast tissue. During puberty, the production of female hormones (estrogens) causes a girl’s breast to develop glands that produce milk (lobules), ducts that will carry milk, and supporting fatty tissue. As a boy enters puberty, he isn’t exposed to these growth-inducing hormones, but rather male hormones that restrict his breasts from developing. This might explain why breast cancer is less common in men than in women.
When male breast cancer spreads, it usually reaches the lymph nodes under the arm first. Lymph nodes are small, bean-shaped organs that contain different types of cells, including immune cells, which help the body fight infections and cancer.
The axillary (armpit) lymph nodes carry lymph — a clear fluid containing immune cells —away from the breast via lymphatic vessels, fine tubes that are similar to blood vessels. By traveling in the lymph, cancer cells that have detached from a breast tumor can reach the axillary lymph nodes and begin to grow new tumors.
The status of axillary lymph nodes is an important prognostic factor for male breast cancer. By testing to see if a patient’s cancer has reached the lymph nodes, doctors can estimate the risk that the cancer has or is about to spread to other parts of the body, such as the bones or lungs, and recommend an appropriate treatment plan.
The most common risk factors associated with male breast cancer include exposure to high levels of the hormone estrogen, radiation, and a family history of female or male breast cancer.
Several medical conditions can increase levels of the hormone estrogen and therefore increase a man’s risk of developing breast cancer.
These include obesity, testicular atrophy and liver disease. Men born with Klinefelter’s syndrome — a rare genetic condition characterized by the presence of an extra X chromosome in most cells — also have hormonal imbalances, and some studies suggest that these men have an increased risk of breast cancer.
Men taking high doses of estrogens as part of a sex-change procedure may be increasing their risk of developing breast cancer as well. Estrogen-related drugs, which sometimes are used in the treatment of prostate cancer, may increase risk, although this risk is minor in comparison with the benefits of treatment for prostate cancer.
Men who are treated with radiation therapy for cancers in the chest, such as lymphoma, have an increased risk of developing breast cancer.
About one in five men with breast cancer have a male or female parent, sibling, or child with the disease. In both women and men, inherited forms of breast cancer are linked to mutations (changes) in the BRCA1 or BRCA2 genes, which are passed on from one generation to the next. For unknown reasons, male breast cancer is much more commonly associated with BRCA2 than BRCA1 mutations, while in women mutations in both genes are equally associated with breast cancer risk. Mutations in BRCA2 are believed to account for about one in ten cases of male breast cancer.
If a woman inherits a mutation in BRCA1 or BRCA2 from her mother or father, she will have a markedly increased risk of developing breast and or ovarian cancer. These mutations are also associated with an elevated breast cancer risk in men, as well as prostate cancer.
There is some evidence that other mutations, including those in genes called CHEK2 and PTEN, may be associated with breast cancer in men.