Approximately 5–10% of all cancers are hereditary — caused by inherited genetic mutations that significantly increase the lifetime risk of developing specific cancer types. For individuals who carry these mutations, the difference between knowing and not knowing can be the difference between early detection and late-stage diagnosis.
What "hereditary cancer" means
Most cancers are sporadic — they arise from acquired mutations that accumulate over a lifetime due to environmental factors, aging, and random replication errors. Hereditary cancers are different. They are caused by germline mutations — variants present in every cell of the body from birth, inherited from one or both parents.
Carrying a hereditary cancer mutation does not mean you will develop cancer. It means your baseline risk is significantly elevated compared to the general population. With that knowledge comes the ability to act: increased surveillance, earlier screening, risk-reducing interventions, and informed family planning.
The major hereditary cancer syndromes
While dozens of hereditary cancer syndromes have been identified, several account for the majority of hereditary cancer cases:
- BRCA1 / BRCA2 (Hereditary Breast and Ovarian Cancer Syndrome): Women with pathogenic BRCA1 variants have a 55–72% lifetime risk of breast cancer and 39–44% risk of ovarian cancer. BRCA2 variants carry a 45–69% breast cancer risk and 11–17% ovarian cancer risk. Men with BRCA2 mutations also have an elevated risk of prostate and breast cancer.
- Lynch Syndrome (Hereditary Nonpolyposis Colorectal Cancer): Caused by mutations in mismatch repair genes (MLH1, MSH2, MSH6, PMS2, EPCAM). Lynch syndrome carriers have up to an 80% lifetime risk of colorectal cancer and significantly elevated risks of endometrial, ovarian, gastric, and urinary tract cancers.
- Li-Fraumeni Syndrome (TP53): One of the most penetrant cancer predisposition syndromes. TP53 mutation carriers have a near-100% lifetime risk of developing cancer, with early onset and multiple primary tumors common.
- CHEK2: Moderate-penetrance variants associated with 2–3x increased risk of breast cancer, as well as elevated risks of colorectal and prostate cancer.
- Cowden Syndrome (PTEN): Associated with increased risks of breast, thyroid, endometrial, and colorectal cancer, along with characteristic non-cancerous features.
What consumer tests miss
Consumer DNA tests from companies like 23andMe check for a small number of specific BRCA1/BRCA2 mutations — typically the three Ashkenazi Jewish founder mutations. This covers approximately 2% of all known pathogenic BRCA variants. A negative result from a consumer test does not mean you don't carry a BRCA mutation — it means you don't carry one of the three that were tested.
This distinction is critically important. Studies have shown that consumer BRCA tests miss the vast majority of carriers, particularly in non-Ashkenazi populations. Patients who receive a "negative" consumer result may incorrectly assume they are not at elevated risk, potentially delaying appropriate clinical screening.
What whole genome sequencing covers
Whole genome sequencing reads the complete sequence of every cancer predisposition gene — not just a handful of known mutations. For BRCA1 and BRCA2 alone, WGS can detect thousands of possible variants, including:
- Point mutations (single nucleotide changes)
- Small insertions and deletions (frameshifts)
- Large structural rearrangements
- Deep intronic variants that affect gene splicing
Beyond BRCA, Dante Labs' whole genome sequencing evaluates variants across all clinically significant hereditary cancer genes — including Lynch syndrome genes, TP53, CHEK2, PALB2, ATM, CDH1, PTEN, and dozens more — in a single test.
The family dimension
Hereditary cancer mutations are, by definition, familial. If a pathogenic variant is identified in one family member, every first-degree relative has a 50% chance of carrying the same mutation.
This creates a cascade screening opportunity. A single whole genome sequence can identify a variant that enables targeted testing for parents, siblings, and children — potentially identifying carriers before they develop symptoms and enabling early intervention.
For families with a strong cancer history — multiple relatives affected, cancers at young ages, rare cancer types — genetic testing is not optional. It is a clinical standard of care recommended by the National Comprehensive Cancer Network (NCCN) guidelines.
What to do with a positive result
A positive hereditary cancer result is not a diagnosis. It is actionable risk information that enables a personalized management plan:
- Enhanced surveillance: Earlier and more frequent screening (e.g., annual breast MRI for BRCA carriers starting at age 25)
- Risk-reducing surgery: Prophylactic mastectomy or oophorectomy reduces breast and ovarian cancer risk by 90–95% in high-risk carriers
- Chemoprevention: Medications like tamoxifen can reduce breast cancer risk in certain high-risk individuals
- Informed family planning: Preimplantation genetic testing (PGT) can prevent transmission of high-penetrance variants to the next generation
- Clinical trial access: Many targeted cancer therapies (e.g., PARP inhibitors for BRCA-positive cancers) require confirmed genetic status
The bottom line
Hereditary cancer screening is not about predicting the future. It is about having the information needed to change it. The mutations are already in your genome — the only question is whether you know about them.