Genome Medical

Is hereditary cancer passed down by both parents equally?

By November 17, 2021 Reproductive
Cancer ribbons

Yes, you can inherit breast cancer from your father, prostate cancer from your mother, and vice versa. Here’s why.

“I look most like my dad, and he suffered from a heart attack early in life, so I will likely have a heart attack as well.”

I have heard iterations of this statement in many genetic counseling sessions. When our interests, features or characteristics more closely align with one side of our family, it’s common to feel like we might have also inherited the same health traits and risks for certain diseases from that side of the family. However, we each inherit half of our DNA from each biological parent. Therefore, we are equally as likely to inherit risks for diseases or certain traits from our biological mother’s and father’s sides.

As a cancer genetic counselor, I assess family histories for cancer occurrence in order to make an accurate risk assessment for an individual. Some of the clues that could point to a hereditary cancer syndrome in a family include:

  • cancer diagnosed at early ages (i.e. under the age of 50)
  • multiple family members with cancer on the same side of the family
  • family members with cancer in multiple generations on the same side of the family
  • certain types of cancer, such as ovarian or pancreatic
  • certain patterns of cancer within a family such as breast/ovarian/prostate or uterine/colorectal cancer

Even if someone reports a strong family history of colon cancer on their mother’s side and that is what they are most concerned about, it is important to collect information regarding cancer history on the individual’s father’s side as well.

Consider this example: if your father’s mother (also called your paternal grandmother) had breast cancer and she carries a genetic variant that increases the risk of developing breast and ovarian cancer, there’s a 50% chance your father inherited this variant  from his mother. Although many cancer predisposition genes increase cancer risks for both men and women, the increased cancer risks for men may not be as high as the risk for breast and/or ovarian cancer in women. Therefore, your father may carry this genetic variant from his mother but may never develop cancer. If your father has four brothers and no sisters, there’s an even higher likelihood that no one in your father’s generation has developed a cancer related to the genetic variant that runs in your family. Let’s say your father did inherit the variant from his mother, then there’s a 50% chance you inherited the variant from your father. This could lead to earlier/more frequent screening or surgical cancer prevention options. Additionally, if you are of reproductive age, this information could impact family planning.

Since we inherit 50% of our DNA from each side of our family, a family history of breast cancer, particularly diagnosed younger than age 50, and/or ovarian cancer on either side of the family is equally important for your health. If there is a genetic variant associated with increased cancer risk on your father’s side, you are just as likely to inherit the genetic variant as if it were on your mother’s side of the family.

Collecting family health history can be difficult; some family members may not feel comfortable sharing their personal health information. So how can you best prepare for a genetic counseling session? You can find some general tips on a previous blog post here. (link to Shannon Wieloch’s previous blog post). Your genetic counselor will ask if you know what types of cancer family members have had, the approximate age at which they were diagnosed, and if relevant, what kind of treatment they underwent (i.e. a mastectomy after a breast cancer diagnosis). Sharing this information with a genetic counselor can help inform your risk for developing cancer and identify potential hereditary cancer syndromes.