Although breast cancer is rare in men, it does occur: The American Cancer Society estimates that 1,400 new cases of male breast cancer will be diagnosed this year.
The strongest risk factors for male breast cancer are those thought to alter the hormonal balance in men. Testicular atrophy or trauma, sterilization, infertility, and liver disease are all associated with a higher risk of breast cancer. A history of radiation exposure, particularly to the chest wall (common in the treatment of Hodgkin's disease), has also been identified as a risk factor for the development of breast cancer in both males and females.
While most cases of male breast cancer occur in men with no known risk factors, a family history of breast cancer is a significant risk factor. Two genes, BRCA1 and BRCA2, have been linked to families with higher rates of breast cancer and ovarian cancer. When a woman inherits an altered form of one of these genes (called a mutation), she has a markedly increased risk of breast cancer and ovarian cancer. This genetic mutation can be inherited from the mother's side of the family or from the father's side. In these families, the risk for a woman developing breast cancer or ovarian cancer in women can approach 90 percent by age 70. Men inheriting BRCA1 or BRCA2 mutations also have an increased risk of breast cancer, although breast cancer is much less common in men. While an increase in male breast cancer is not associated with the BRCA1 gene mutation, the BRCA2 gene mutation does present an increased risk of male breast cancer.
One recent study demonstrated that 15 percent of male breast cancer patients have one or more first-degree relatives with breast cancer. BRCA2 mutations are found in seven percent of men with breast cancer. Other studies here have shown that, similar to female breast cancer, male breast cancers show a high incidence of p53 gene mutations. Mutations of the p53 gene have been observed in nearly half of all human cancers and appear to be related to the most aggressive types of the disease.
Unlike familial breast cancer in women, where the age at diagnosis is frequently younger than that in patients with randomly occurring breast cancer, a family history of breast cancer has not been shown to be associated with a younger age of disease onset in males.
Gynecomastia
There is no conclusive evidence that gynecomastia -- the excessive development of the male mammary glands -- is itself a risk factor for the development of breast cancer. Gynecomastia has been associated with a number of different causes, including altered estrogen-to-androgen hormone levels, liver failure, kidney failure, and the use of some medications. There are some features that help differentiate gynecomastia from breast cancer. Gynecomastia is most frequently found in both breasts. When it is one-sided, most often disc-shaped breast tissue accumulates under the nipple. As with female breast cancers, male breast cancers are more frequently asymmetric and can involve skin dimpling or attachment to the underlying chest muscle. If any of these features are present, a breast tissue biopsy should be done. Mammography and fine-needle aspiration may also be helpful in making a diagnosis.
