The most common risk factors associated with male breast cancer are age, exposure to higher levels of the hormone estrogen relative to the male hormone androgen, radiation, and a family history of female or male breast cancer.
Increased age is the most common risk factor for breast cancer in men. On average, the disease is diagnosed later in men than in women, meaning that most patients are in their late 60s or 70s.
Several medical conditions can increase the level 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 syndrome — a rare genetic condition characterized by the presence of an extra X chromosome in most cells — also have hormonal imbalances. Some studies suggest that these men have an increased risk of breast cancer.
People taking high doses of estrogen as part of male-to-female gender-reassignment may have an increased chance of developing breast cancer as well. Estrogen-related drugs, which sometimes are used in the treatment of prostate cancer, may increase the risk too. This risk is minor in comparison with the benefits of treatment for prostate cancer, however.
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 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. BRCA2 mutations in men are also associated with an increased risk of prostate cancer.
There is some evidence that other mutations — including those in genes called CHEK2, PTEN, and PALB2 — may be associated with breast cancer in men.
Men who are known to be at a high risk for breast cancer because of genetic mutations may wish to participate in RISE (Risk Assessment, Imaging, Surveillance, and Education), MSK’s comprehensive program that includes regular breast exams and imaging so that any cancer developments can be identified and dealt with right away.