Is Cancer Genetic?

Cancer is caused by genetic changes that trigger cells to grow out of control, but it is not usually hereditary. Cancer-causing genetic mutations in segments of DNA can be inherited or, more commonly, acquired over time.

Inherited gene mutations are passed from parents’ reproductive cells (the egg or sperm) to their offspring—and are present in all body cells of the offspring. Acquired genetic mutations, on the other hand, originate in one cell due to things like cell division errors or exposure to carcinogens (cancer-causing substances), like tobacco or radiation.

Most cancers are multifactorial, which means your risk goes up depending on a variety of factors including your genetics, environment, lifestyle, and personal health history. Learn more about cancer genetics and how gene mutations may cause cancer. 

Hereditary Cancer Syndrome 

So, is cancer genetic? In about 5% to 10% of cases, inherited genetic mutations are indeed at the root of increased cancer risk. These are known as hereditary cancer syndromes or germline mutations. 

Certain signs in your family’s medical history may indicate that you have inherited cancer risk. These include:

• Cancer in many generations (like a grandmother, mother, and daughter)
• Multiple cases of the same type of cancer, especially if it is uncommon or rare 
• Cancer at younger ages than usual
• Childhood cancer in siblings
• More than one type of cancer in a single person
• Cancer in a pair of organs (such as both eyes, breasts, or kidneys)
• Cancer in the sex typically not affected (like male breast cancer)

The concern is particularly high if you notice a pattern of cancer in your immediate family or on one side of your family. In this case, many healthcare providers recommend genetic testing to rule out other causes, identify a hereditary cancer syndrome, and better guide your medical decisions in the future. 

Types of Inherited Cancers 

An inherited gene mutation doesn’t guarantee that you’ll develop cancer, but it means that you’re at an increased risk of developing the disease. 

Here are some types of cancer known to be linked to inherited genes:

• Hereditary breast and ovarian cancer syndrome (HBOC) are linked to an inherited mutation in the BRCA1 or BRCA2 gene or others. Breast cancer, ovarian cancer, fallopian tube cancer, primary peritoneal cancer, male breast cancer, pancreatic cancer, and prostate cancer, among others, can be associated with mutations of the HBOC gene. 
• Breast, thyroid, endometrial, and other types of cancer are linked to mutations in the PTEN gene due to Cowden syndrome. 
• Colorectal cancer can be a high risk if you have mutations in several genes, such as MLH1, MSH2, MSH6, and PMS2 due to Lynch syndrome. This mutation also increases the risk of cancers of the endometrium, ovary, stomach, small intestine, pancreas, kidney, ureters, brain, and bile duct. 
• Multiple cancers such as sarcoma, leukemia, brain, adrenal cortex, and breast cancer are linked to inherited mutations in the TP53 gene due to Li-Fraumeni syndrome. 

Acquired Cancer-Causing Mutations 

Acquired cancer-causing mutations, also known as somatic changes, are at the root of most cancers. Sometimes, these mutations happen as a result of exposure to carcinogens. However, they can occur any time a cell divides. 

Factors that Cause Genetic Mutations 

Many environmental and lifestyle factors can contribute to the development of cancer.

These include: 

• Tobacco, which contains a slew of carcinogens, depending on the type, such as nicotine, benzene, and polycyclic aromatic hydrocarbons (PAHs)
• Ultraviolet (UV) radiation from sunlight and tanning beds 
• Alcohol due to damage to the liver, and other changes such as increased levels of estrogen 
• Being overweight or obese, possibly due to inflammation, changes in hormone levels, cell growth, and more 
• Certain infections including human papillomavirus (HPV), human immunodeficiency virus (HIV), and hepatitis B or hepatitis C 
• Exposure to asbestos, coal, radon, or other carcinogens where you work or live
• Advancing age 

Genetic Testing for Cancer 

If you’re concerned about your cancer risk due to your family history, a healthcare provider can help you determine whether genetic testing for cancer is right for you. Depending on your individual situation, the results of your genetic testing may empower you to take steps to reduce your risk or to schedule cancer screenings for earlier detection and treatment. 

That said, genetic testing is not always helpful and can’t predict the future—which means your test results could also lead to stress and anxiety or even a misunderstanding of the results. According to the American Cancer Society (ACS), it’s best to talk to a trained genetic counselor rather than diving in on your own with an at-home genetic test.

Testing for Inherited Genes 

With a referral from your healthcare provider, you can meet with a specialist for genetic counseling. If you determine you want to have genetic testing done, you can send off a blood or saliva sample to a lab. There, it can be examined for changes in your DNA that could indicate genetic mutations for different types of cancer. 

Your genetic counselor can help you review your results to learn more about your hereditary cancer risk and next steps to consider to lower your cancer risk. 

Testing for Mutations to Cancer 

If you’ve recently been diagnosed with cancer, your healthcare providers may also recommend a different form of genetic testing known as genomic testing which examines the genetic makeup of cancer cells specifically.

These tests can come with many benefits. They may help better determine your prognosis, risk of cancer recurrence, and which treatments will (or won’t) work most effectively for your cancer type.

A Word From Verywell 

While cancer is genetic, the impact of your genes, lifestyle, and environment on your potential cancer risk can be complex and confusing. If someone close to you has recently been diagnosed with cancer or you’re concerned about your family history, ask your healthcare provider about genetic counseling.

With their help, you can empower yourself and gain some peace of mind with tools like genetic testing, lifestyle changes, and regular screenings.