Breast cancer genes can be inherited from either your mother or your father. The mutations that raise breast cancer risk sit on regular chromosomes, not sex chromosomes, so each parent has an equal 50% chance of passing one to their child. The widespread belief that breast cancer “comes from your mother’s side” is a myth, and it’s one that causes many people to overlook important warning signs in their father’s family.
Why Both Parents Carry Equal Risk
Everyone has two copies of each gene: one from each biological parent. The genes most strongly linked to breast cancer, BRCA1 and BRCA2, follow this same pattern. If your father carries a harmful change in one of these genes, you have the same 50% chance of inheriting it as you would if your mother carried it. This applies to all of the known breast cancer susceptibility genes, not just BRCA1 and BRCA2.
A large study in Cancer Epidemiology, Biomarkers & Prevention looked at whether the parent of origin made any difference in actual breast cancer risk. Early results seemed to suggest that inheriting the mutation from your father carried slightly higher risk, but once researchers corrected for referral bias (the fact that families are more likely to be flagged and tested when the mother had cancer), the difference disappeared. There is no conclusive evidence that a BRCA mutation from one parent is more dangerous than the same mutation from the other.
Why Paternal Risk Gets Overlooked
The misconception exists for a practical reason: breast cancer is far more visible on the maternal side. If your mother, maternal aunt, and maternal grandmother all had breast cancer, the pattern is obvious. On your father’s side, the men who carry the mutation often never develop breast cancer themselves, so the gene can pass silently through generations of men without anyone noticing. Your father could carry a BRCA2 mutation, never get breast cancer, and pass it directly to you.
That’s why your father’s female relatives matter so much. If your paternal grandmother, a paternal aunt, or a paternal cousin had breast or ovarian cancer, that history is just as significant as cancer on your mother’s side. Multiple breast cancers in your father’s family could indicate a genetic mutation passing through that line. Prostate and pancreatic cancers on either side of the family are also relevant, since the same BRCA mutations raise the risk for those cancers too.
How BRCA Mutations Affect Risk
More than 60% of women who inherit a harmful BRCA1 or BRCA2 change will develop breast cancer during their lifetime, compared to about 13% of women in the general population. The risk is roughly four to five times higher than average, regardless of which parent the mutation came from.
These same mutations raise the risk for several other cancers:
- Ovarian cancer: 39%–58% lifetime risk with BRCA1, 13%–29% with BRCA2, versus about 1.1% in the general population.
- Pancreatic cancer: Up to 5% with BRCA1, 5%–10% with BRCA2, versus about 1.7% in the general population.
- Prostate cancer: 7%–26% with BRCA1, 19%–61% with BRCA2 by age 80, versus about 10.6% in the general population.
This is important context when you’re looking at family history. A father with aggressive prostate cancer and a paternal aunt with ovarian cancer could point to the same inherited mutation that also raises breast cancer risk.
Men Can Get Breast Cancer Too
Men with BRCA mutations face a small but real risk of breast cancer. Male BRCA1 carriers have a 1%–5% chance, and male BRCA2 carriers have a 5%–10% chance, compared to 0.1% for the average man. That means a BRCA2 mutation raises a man’s breast cancer risk by 50 to 100 times, even though the absolute numbers remain relatively low. When a man in your family has had breast cancer, it’s one of the strongest signals that a genetic mutation may be present.
Beyond BRCA: Other Inherited Genes
BRCA1 and BRCA2 get the most attention, but researchers have identified at least 13 genes linked to increased breast cancer risk. These include PALB2, ATM, CHEK2, TP53, CDH1, PTEN, and STK11, among others. Each carries a different level of risk, from moderate to very high. TP53 mutations, for example, are associated with Li-Fraumeni syndrome, which dramatically raises the risk of multiple cancer types starting at a young age.
Every one of these genes follows the same inheritance pattern: one copy from each parent, a 50% chance of passing it on. None of them are sex-linked, so none of them preferentially come from your mother. Dozens of additional genes are still under investigation, including BRIP1 and MUTYH, which may also play a role.
How to Assess Your Family History
When evaluating your risk, collect cancer history from both sides of your family going back at least two generations. Pay attention to more than just breast cancer. Ovarian, pancreatic, and prostate cancers in close relatives can all point toward the same inherited mutations. Cancer diagnosed at a younger age (before 50) or multiple cancers in the same person are particularly significant.
On your father’s side specifically, look at his sisters, his mother, and his maternal aunts. These are the women who may have expressed a mutation that your father carried silently. If any of them had breast or ovarian cancer, that information is just as clinically meaningful as the same cancers on your mother’s side. If your father himself had breast cancer or early-onset prostate cancer, both are strong indicators worth discussing with a genetic counselor.
Genetic testing can identify mutations in BRCA1, BRCA2, and the other known susceptibility genes. Testing is typically recommended when your personal or family history suggests a hereditary pattern. If you’ve been focused only on your mother’s side, expanding your view to include your father’s relatives could change whether testing is appropriate for you.