Genetics and Family History

Genetics and Inherited Risk

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Knowing more about your genetics can help inform you about your health

You might find yourself asking: Why me? Was it genetics? Something in my environment? Just bad luck?

Sometimes, the answer lies in family history. A small number of people carry an inherited gene mutation that increases their risk for breast cancer. In other cases, it may be linked to hormones or exposure to a carcinogen (a cancer-causing agent), like radiation.

But for many, there’s no clear explanation, and that uncertainty can be frustrating.

What are genes and why do they matter?

Genes are tiny pieces of information made of DNA that tell your body how to function. You get half of your genes from each parent, and you pass them on to your children.

Think of each gene as a recipe with instructions for your body to make something it needs, like a specific protein. If there’s a change or error in the instructions (called a mutation), it can affect how your body works and may increase your risk of developing certain diseases, including cancer.

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What You Need to Know About Family History

Your family history is the single biggest risk factor for developing breast cancer at a young age, especially if a close relative like a parent, grandparent, or sibling was also diagnosed early.

Roughly 5–10% of all breast cancers are hereditary, caused by gene mutations passed down through a parent.

Understanding Inherited Risk

You inherit two sets of chromosomes, made up of genes, protein, and DNA, one from each parent. If there’s a genetic mutation in the genes that protect against breast cancer, that risk can be passed from generation to generation.

Two genes in particular—BRCA1 and BRCA2—are closely linked to increased risk. These genes are located on chromosomes 17 and 13. Around 10% of young adults with breast cancer carry a BRCA1 or BRCA2 mutation. While they are the most well-known genes linked to breast cancer, they’re not the only ones that can increase risk. Other genes may also play a role. Talking with a genetic counselor can help you understand your family history, assess your personal risk, and make informed decisions about screening and prevention.

These mutations can raise your lifetime breast cancer risk to 50–85% and also increase your risk of ovarian cancer.

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You may have a higher chance of carrying a BRCA mutation or another gene linked to hereditary breast cancer if you:

Have Ashkenazi Jewish, Dutch, or other higher-risk ancestry
Were diagnosed with breast cancer before age 50
Have had breast cancer in both breasts
Have a personal or family history of ovarian cancer
Were diagnosed with triple negative breast cancer (cancers that do not have receptors for estrogen, progesterone, or a protein called HER2 )
Have a family history of pancreatic cancer
Have a family history of metastatic prostate cancer
Have Ashkenazi Jewish, Dutch, or other higher-risk ancestry