While breast cancer is much more common in women, it can occur in men too. About 0.01% of all breast cancer cases in the United States are in men.[1] Women have more breast tissue than men, making it more likely that cancer will develop in this area. However, since men still have some breast tissue, cancer can form there.[2] Like in women, the most common types of breast cancer[MB1] in men are invasive ductal carcinoma, invasive lobular carcinoma, and ductal carcinoma in situ.[1]

Benign (noncancerous) breast tumors are common in women, but very uncommon in men. The most common breast disorder in men is gynecomastia which causes an increase in breast tissue (not a tumor). Gynecomastia usually occurs as a result of a hormone imbalance and is therefore more common in pubescent boys or older men. Other factors that can lead to gynecomastia are obesity, tumors or diseases of the endocrine glands which produce hormones, diseases of the liver, and certain medications because all of these things can affect hormone balance and increase the levels of estrogen in a man’s body.[2]

Genetics can also increase a man’s chance of getting breast cancer. The BRCA1 and BRCA2 (breast cancer 1 and 2) genes [MB2] are the most common inherited mutations that lead to breast cancer.[3] Having a BRCA mutation increases the risk of a man getting breast cancer to 8% by the age of 80, a rate that is 8 times greater than average.[4] Additionally, a genetic condition called Klinefelter syndrome can increase the risk of a man getting both gynecomastia and breast cancer. This condition occurs when a man’s cells have one Y chromosome and at least two X chromosomes. Typically, men’s cells contain a Y chromosome and an X chromosome, while women’s cells contain two X chromosomes. Klinefelter syndrome can increase the risk of a man getting breast cancer by 20-60 times the average. Gynecomastia is often caused by Klinefelter syndrome because it can increase the levels of estrogen in a man’s body.[5]

Other factors that can increase the risk of a man getting breast cancer are radiation exposure to the chest, alcoholism, liver disease, estrogen treatment, obesity, and testicular conditions. Risk of developing breast cancer is greater for older men and men with a family history of breast cancer. The average age that men are diagnosed with breast cancer is 72.[5]

References

1.     Breast Cancer in Men https://www.cdc.gov/cancer/breast/men/index.htm (accessed Jun 16, 2021).

2.     What Is Breast Cancer in Men? https://www.cancer.org/cancer/breast-cancer-in-men/about/what-is-breast-cancer-in-men.html (accessed Jun 16, 2021).

3.     How Gene Mutations Cause Cancer https://www.hbocsociety.org/how-gene-mutations-cause-cancer.html (accessed Jun 15, 2021).  

4.     Men With BRCA Mutations Have Much Higher Risk of Cancer https://www.breastcancer.org/research-news/brca-mutations-up-cancer-risk-in-men (accessed Jun 15, 2021).

5.     Risk Factors for Breast Cancer in Men https://www.cancer.org/cancer/breast-cancer-in-men/causes-risks-prevention/risk-factors.html (accessed Jun 16, 2021).

 [MB1]Link to ‘types of breast cancer’ article

 [MB2]Link to ‘BRCA gene mutations’ article