All men have breast tissue, as it one of the tissue types present at birth. When breast cells become cancerous, the change is often related to multiple genetic mutations that accumulate in a cell until normal control of cell growth is lost. According to the American Cancer Society, although risk factors for male breast cancer exist, most breast cancers in men have no known cause. Factors that underlie male breast cancer include increased hormonal levels and genetic mutations.
Hormone Levels
Breast cells normally grow and divide in response to hormones such as estrogen. Taking estrogen-related drugs, such as those used in hormone therapy for prostate cancer, thereby increase the chance of male breast cancer. Obesity increases the number of fat cells in the body, which convert androgens into estrogen. An increased amount of estrogen related to obesity increases risk of breast cancer for men.
The liver breaks down hormones, and diseases that impede normal liver function lead to hormone imbalance. Cirrhosis, a scarring of the liver, reduces male hormones and increases female hormones, thereby increasing the risk for male breast cancer. Klinefelter's syndrome, a genetic disease characterized by having more than one copy of the X chromosome, causes abnormal development of the testicles and results in lower levels of male hormones and more female hormones. This condition, like cirrhosis, leads to an increased risk for male breast cancer.
Although the relationship is not well understood, alcohol appears to increase the risk for male breast cancer. According to the Mayo Clinic, the link occurs with excessive drinking. Yet a study published in late 2008 in the Journal of the National Cancer Institute reported that alcohol was unrelated to male breast cancer risk and that the differences between male breast cancer and female breast cancer and alcohol consumption reflected differences in androgen levels.
Acquired Genetic Mutations
Most DNA mutations related to male breast cancer occur during life, although the causal relationship remains unclear. Aging allows for DNA mutations to accumulate, and male breast cancer commonly occurs in men after the age of 60.
Chemical exposure might also be a cause of DNA mutations leading to breast cancer. Yet the American Cancer Society reports that studies have not identified any chemicals responsible for male breast cancers.
Radiation treatments to the chest, such as those used to treat cancers in the chest, increase the chance for genetic mutations and the development of male breast cancer later in life. This exposure accounts for a small number of male breast cancers.
Inherited Genetic Mutations
Having a family member with breast cancer increases a man's risk of developing breast cancer. Inherited changes in a gene labeled BRCA2 account for about 10 percent of male breast cancers. The lifetime breast cancer risk for men with BRCA2 mutations reaches as high as 10 percent. According to the American Cancer Society, mutations in another gene, labeled BRCA1, also increase the lifetime risk of breast cancer to 1 percent in men, more commonly among Jewish men.
References
- American Cancer Society: Detailed Guide: Breast Cancer in Men Do We Know What Causes Breast Cancer in Men?
- Mayo Clinic: Diseases and Conditions: Male Breast Cancer: Basics: Risk Factors
- "Journal of the National Cancer Institute"; Prospective evaluation of risk factors for male breast cancer; L.A. Brinton, D.A. Richesson, G.L. Gierach, J.V. Lacey Jr, Y. Park, A.R. Hollenbeck and A. Schatzkin; October 2008
