Cancer is the result of DNA mutations which can be inherited or developed as a result of a variety of factors such as weight and lifestyle choices, environmental exposures, genetics, or simply aging. Mutations that cause breast cancer are most often acquired, but the BRCA1 and BRCA2 (breast cancer 1 and 2) genes are the most common inherited mutations that lead to breast cancer.[1] Every person has the BRCA1 and BRCA2 genes, and these genes help prevent breast cancer by repairing any mutations that occur. For people who have a mutation in this gene, however, breast cancer is much more likely to develop because this repair mechanism no longer works. While the average rate of women who will develop breast cancer in their lifetime is 12%, the percentage of women who will develop breast cancer before the age of 70 increases to 55-65% for women with a BRCA1 mutation and 45% for women with a BRCA2 mutation.2 Women with BRCA mutations are more likely to develop ovarian cancer as well.[3]

Breast cancer is rare in men but 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. BRCA mutations in men also increase the risk of prostate cancers, particularly BRCA2 mutations. Men with a BRCA mutation also might be at a slightly greater risk of additional cancers such as skin or digestive tract cancer. Overall, men with BRCA mutations developed 8 times more cancers than average.[4]

            About 0.25% of the population has a BRCA mutation. Women with a BRCA mutation who develop breast cancer are often younger than average and are more likely to develop triple-negative breast cancer (TNBC), a more aggressive and difficult to treat type. This mutation also makes breast cancer recurrence more common.[2] Genetic testing can be done to look for a BRCA mutation and is typically recommended for those with a personal or family history of breast or ovarian cancer.[3] Some examples of when genetic testing would be recommended are if you have a personal history of:

            There are other inherited mutations that can lead to a greater risk of developing breast cancer. Some of these include the ATM, TP53, CHEK2, PTEN, CDH1, STK11, and PALB2 genes.[5]

References

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

2.     BRCA: The Breast Cancer Gene https://www.nationalbreastcancer.org/what-is-brca (accessed Jun 15, 2021).

3.     BRCA gene test for breast and ovarian cancer risk https://www.mayoclinic.org/tests-procedures/brca-gene-test/about/pac-20384815 (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).