About 10% of all cancers are hereditary, caused by gene mutations passed from parent to child. The other roughly 70% are sporadic, driven by DNA damage that accumulates over a lifetime from environmental exposures, lifestyle factors, or simple chance. The remaining cases fall somewhere in between, where inherited traits raise susceptibility but don’t guarantee cancer on their own. Knowing which cancers have a strong genetic component can help you understand your own risk and whether genetic testing makes sense for your family.
How Inherited Cancer Differs From Sporadic Cancer
Every cancer involves DNA mutations, but the origin of those mutations matters. In hereditary cancer, the critical mutation exists in a parent’s egg or sperm cell, so every cell in the child’s body carries it from birth. These are called germline mutations. You only need one additional hit to a related gene for a tumor to start forming, which is why hereditary cancers often appear earlier in life and sometimes in multiple organs.
Sporadic cancers work differently. The mutations happen after conception, in ordinary body cells, through things like UV radiation, tobacco smoke, or random copying errors as cells divide. These mutations can’t be passed to children because they never existed in reproductive cells. When someone develops cancer with no family history, this is almost always the explanation.
Breast and Ovarian Cancer (BRCA1 and BRCA2)
The most widely known genetic cancer risk comes from mutations in the BRCA1 and BRCA2 genes. More than 60% of women who inherit a harmful change in either gene will develop breast cancer during their lifetime, compared to about 13% of women in the general population. The ovarian cancer numbers are even more striking: women with a BRCA1 mutation face a 39% to 58% lifetime risk of ovarian cancer, while the general population risk is just 1.1%. BRCA2 mutations carry a 13% to 29% ovarian cancer risk.
BRCA2 also raises the risk of prostate cancer and pancreatic cancer. Male breast cancer, though rare overall, is strongly linked to BRCA mutations and is considered an immediate indication for genetic testing. These genes normally help repair damaged DNA, so when they’re broken, cells accumulate errors much faster than they should.
Several other genes contribute to hereditary breast cancer risk at lower levels. Mutations in PALB2, CHEK2, and ATM each account for a smaller slice of cases but still raise lifetime risk meaningfully above the general population.
Colorectal Cancer
Two major inherited conditions drive genetic colorectal cancer: Lynch syndrome and familial adenomatous polyposis (FAP).
Lynch syndrome is caused by mutations in genes responsible for repairing mismatched DNA during cell division. The four primary genes involved are MLH1, MSH2, MSH6, and PMS2. People with Lynch syndrome don’t just face elevated colorectal cancer risk. They also have higher lifetime rates of uterine, ovarian, stomach, small intestine, urinary tract, brain, and skin cancers. Lynch syndrome is one of the two most common hereditary cancer syndromes overall.
FAP takes a different path. A mutation in the APC gene causes hundreds to thousands of polyps to form in the colon, typically starting around age 16. Without surgical removal of the colon, colorectal cancer is essentially inevitable. By age 45, 87% of untreated individuals with classic FAP have developed cancer, and by 50, that figure reaches 93%. A milder form, called attenuated FAP, carries a 70% lifetime risk with cancer appearing on average between ages 50 and 55.
Childhood Cancers With a Genetic Link
Retinoblastoma, the most common eye cancer in children, has one of the clearest genetic patterns of any cancer. About 40% of cases are hereditary, caused by a mutation in the RB1 gene on chromosome 13. The defective gene can come from either parent. Children with the hereditary form often develop tumors in both eyes, while the non-hereditary form almost always affects just one. Retinoblastoma occurs in roughly 1 in every 20,000 births.
Li-Fraumeni syndrome, caused by mutations in the TP53 gene, is another important hereditary condition in children. TP53 normally acts as a master tumor suppressor, stopping damaged cells from dividing. When it’s broken from birth, the cancer risks are broad and early: breast cancer in women under 30, pediatric cancers of several types, and bone cancers called osteosarcomas. About 8% of pediatric cancers are linked to TP53 mutations.
Kidney, Thyroid, and Pancreatic Cancers
Von Hippel-Lindau syndrome, caused by mutations in the VHL gene, raises the risk of clear cell renal cell carcinoma (a specific type of kidney cancer), pancreatic neuroendocrine tumors, and tumors of the adrenal glands. People with this syndrome also commonly develop cysts in the kidneys, pancreas, and genital tract, along with characteristic blood vessel tumors called hemangioblastomas in the brain and spinal cord.
Thyroid cancer has its own hereditary pathway through multiple endocrine neoplasia type 2 (MEN2), driven by mutations in the RET gene. This syndrome is strongly associated with medullary thyroid carcinoma, a form that accounts for a small percentage of all thyroid cancers but runs powerfully in affected families. A related condition, MEN1, affects the parathyroid glands, pancreatic hormone-producing cells, and the pituitary gland.
Pancreatic cancer risk is elevated by several hereditary syndromes. Beyond BRCA2 and VHL, mutations in CDKN2A (also linked to hereditary melanoma) and STK11 (the gene behind Peutz-Jeghers syndrome) both increase pancreatic cancer susceptibility. Peutz-Jeghers syndrome raises risk across multiple organs, including the breast, colon, stomach, and pancreas.
Stomach, Skin, and Other Cancers
Hereditary diffuse gastric cancer, caused by mutations in the CDH1 gene, accounts for roughly 7% of diffuse-type stomach cancers. This gene also modestly increases the risk of lobular breast cancer. Cowden syndrome, driven by PTEN gene mutations, produces both benign and malignant tumors across the breast, thyroid, uterus, skin, kidneys, and colon.
Gorlin syndrome, linked to the PTCH1 gene, leads to multiple basal cell skin cancers often starting at a young age, along with jaw cysts and an elevated risk of a childhood brain tumor called medulloblastoma. Melanoma risk rises with CDKN2A mutations, particularly in families where multiple members develop melanoma at young ages.
Signs That Cancer in Your Family May Be Genetic
Certain patterns suggest a hereditary syndrome rather than bad luck. Cancer diagnosed at an unusually young age is one of the strongest signals, particularly breast cancer before 45 or colorectal cancer before 50. Multiple family members on the same side with the same cancer type, or one person developing cancer in multiple organs, both raise suspicion. Rare cancers like male breast cancer, medullary thyroid carcinoma, or bilateral retinoblastoma in a child point strongly toward a genetic cause.
Triple-negative breast cancer diagnosed before age 60 is considered an automatic indication for genetic testing. A family history of ovarian cancer at any age, or multiple generations affected by colon and uterine cancers together, warrants evaluation for Lynch syndrome.
What Genetic Testing Actually Involves
Clinical genetic testing uses next-generation sequencing to read the full coding regions of genes associated with hereditary cancer. A typical multi-gene panel covers BRCA1, BRCA2, TP53, PTEN, the Lynch syndrome genes, APC, and others, often analyzing dozens of genes from a single blood or saliva sample. These tests also look for large deletions or duplications that simpler methods miss.
Direct-to-consumer tests like 23andMe work very differently. They check only a handful of preselected DNA positions rather than sequencing entire genes. A study published in Genetics in Medicine found that 40% of variants flagged in direct-to-consumer raw data turned out to be false positives when checked with clinical-grade methods. For example, 23andMe’s Parkinson’s test checks just one variant in each of two genes. A clean result from a consumer test does not rule out a hereditary cancer syndrome, and a flagged result needs confirmation through a clinical laboratory before any medical decisions are made.
If your family history fits the patterns above, a genetic counselor can help determine whether formal testing is appropriate and interpret the results in the context of your specific family tree.