Is Cancer a Genetic Disease? Hereditary Risk & Genetic Testing Guide

Introduction

Cancer can be confusing, especially when people talk about genes. Some people think that if cancer runs in the family, they will definitely get it. Others believe cancer happens randomly and has nothing to do with genes. The truth lies somewhere in the middle.

Most cancers develop from gene changes that happen during the lifetime of an individual due to factors such as aging, lifestyle, and environment, though some cancers can be inherited from parents^1,2. However, cancer itself doesn’t pass from parents to children, and the changes in cancer cells also aren’t passed down. But for certain cancers, parents can pass on some genes that increase the chance of developing that cancer in the offspring (subsequent generation)¹. Understanding this helps people know their risk better and take appropriate measures.

In this blog, we will explore whether cancer is a genetic disease or not, explain the difference between somatic and hereditary cancers, and discuss how family history and genetic testing can help identify individuals at a higher risk.

Is Cancer Genetic?

Cancer is a genetic disease, but it is not always inherited. Cancer develops when specific genes undergo mutations (changes) that affect how cells grow, divide, and repair themselves. These mutations can cause cells to proliferate uncontrollably, resulting in cancer cell formation. These genetic changes are the root cause of all cancers¹.

Genetic changes can happen in two different ways:

1. Somatic Cancer (Sporadic Mutations)

This is the most common type. Here, gene changes occur during a person’s lifetime. They are not present at birth and are not handed down to the generations. These genetic changes or mutations may be caused by aging, environmental exposures (such as pollution and radiation), lifestyle factors (such as smoking, poor diet, or lack of exercise), infections, etc^1,2.

2. Hereditary or Inherted Cancer (Germline Mutations)

This type is less common (only up to 10% of cancer are caused by inherited gene changes)¹. Here a person acquires a gene mutation from their parents. This mutation is present in their cells from early life and can increase the risk of certain cancers. These inherited changes can also be passed on to the next generation from father’s sperm or mother’s egg (germ cells). Examples of hereditary cancer syndromes include BRCA1/BRCA2-related breast and ovarian cancer and Lynch syndrome (an inherited condition that increases a person’s risk of developing certain cancers, especially colon and endometrial cancer, at an early age)³.

So, genetic mutations are responsible for the occurrence of all cancers, but only a small percentage of cancers occur due to certain genes being passed down from parents during conception.

Types of Genetic Changes that Cause Cancer

Cancer can develop due to different types of changes in our genes. These changes affect how cells grow and behave. Here are the main types:

• Gene Mutation (Small Changes in DNA): This is the most common type of change. Our DNA serves as an instruction guide for how cells should function. A small error in this guide such as minor additions, deletions or changes in DNA sequence can affect how a gene functions (point mutations). As a result, cells may begin to grow or divide abnormally, potentially leading to cancer¹. However, more than one important mutation of this type is usually needed for cancer to develop.
• Gene Amplification (Too Many Copies of a Gene): Sometimes the cell generates additional copies of a gene, like having the same instruction repeated many times. This can cause the cell to overproduce particular proteins, which can result in faster cell division, avoidance of cell death (apoptosis), and support new blood vessel formation, thereby increasing the risk of cancer⁴.
• Gene Deletion (Loss of a Gene): In this case, a part of the DNA or even a whole gene is missing or lost. Some genes (such as tumour suppressor genes) normally act like “brakes” that slow down cell growth and keep it under control. When these genes are lost or inactivated, this control is stopped, and cells can grow and divide uncontrollably causing cancer⁵.
• Chromosomal Changes (Large-Scale DNA Changes): These changes affect bigger sections of DNA, not just small parts. Large sections of chromosomes (which carry many genes) can be rearranged, duplicated, or lost. This disrupts normal cell function and lead to cancer⁶.

Signs You May Have a Hereditary Cancer Risk

The following are some signs which say you may have a hereditary cancer:

• Cancer diagnosed at a very young age than usual (before the age of 40-50). Example: premenopausal breast cancer
• Having two or more different, separate cancers at different times. Example: Colorectal and endometrial cancer
• Cancer occurring in both organs (bilateral cancer). Example: cancer in both breasts, or both kidneys
• Same kind of cancer seen in several family members, especially close relatives. Example: Breast cancer occurring in mother, daughter and sister
• Cancer developing in multiple generations.
• Occurrence of rare types of cancer. Example: retinoblastoma, ocular melanoma, duodenal cancer, etc
• Unusual types of cancer. Example: Breast cancer in male
• A cancer having a rare or unusual cell type when seen under the microscope. Example: Medullary thyroid cancer
• A rare cancer detection with a birth defect. Example: A child with kidney-related birth defects developing Wilms tumour (paediatric kidney cancer)
• A known genetic risk already exists in the family. Example: BRCA1/BRCA2 mutants that cause breast cancer⁷

Note: These signs don’t guarantee that cancer is hereditary, but they may indicate a higher risk and the need for medical advice or genetic testing.

What is Genetic Testing for Cancer?

Genetic testing in cancer is usually done to detect the presence of inherited gene mutations that increase the risk of developing certain type of cancers (presence of germline mutations). Sometimes, if a person is already diagnosed with cancer, genetic testing may be done to check for the gene mutations associated with the cancer (tumour or somatic genetic testing). There are numerous types of genetic tests available now, and many more are still being developed⁸.

For predicting cancer risk, genetic testing checks for the presence of specific genes that may raise a person’s chance of getting a cancer. It mainly helps to:

• Identify Hereditary Cancer Risk Early: Testing can detect if a person carries gene mutations linked to cancers such as breast, ovarian, or colorectal cancer
• Guide Screening and Prevention: Doctors may suggest earlier or more frequent check-ups, lifestyle changes, or treatments
• Inform Family Members: If a mutation is found, other relatives can also get tested to understand their risk⁸

In somatic (tumour) genetic testing, the DNA of cancer cells is checked to find changes that led to the tumour. These tests do not detect inherited cancer risk but help doctors in the following way:

• Support Treatment Decisions: Testing can help doctors choose targeted therapies or personalized treatment plans
• Prognosis and Monitoring: Testing helps predict the severity of cancer (also risk of other cancers) and the effectiveness of treatments⁸

How is Genetic Cancer Testing Done to Determine Risk of Inherited Cancers?

Genetic cancer testing checks your DNA to find inherited changes that may increase your risk of certain cancers. It is performed through the following steps:

• Pre-test Counselling & Risk Assessment: A doctor or genetic counsellor examines your personal and family history to look for signs of hereditary cancer risk, such as early cancers or multiple affected relatives. Based on this, they determine whether genetic testing is necessary.

• Obtaining Informed Consent: Prior to the test, the doctor explains the benefits, risks, and limits of genetic testing. He may also discuss the potential emotional or psychological effects of the results. You will have the opportunity to ask questions, and a signed consent form is typically necessary before starting.
• Sample Collection: As per the doctor’s advice, a small sample of your body fluid or tissue is collected in a simple and minimal invasive way. These may include blood sample, or sometimes saliva. These will be containing your DNA, which will be analysed for genetic changes.
• Laboratory Analysis: The collected sample is transferred to a specialised laboratory, where experts extract DNA and analyse it. They search for specific gene mutations that are associated with cancer risk. Testing may focus on a particular gene (such as BRCA1/BRCA2) or use a multigene panel to evaluate multiple genes at once.
• Review of Results: The laboratory prepares a detailed report and sends it to your doctor or genetic counsellor. Results are typically available within 1 to 6 weeks (timing can vary depending on the test type and laboratory, for both hereditary and tumour testing). The report may show:
  • A positive result: Means a gene change was found that increases cancer risk.
  • A negative result: Means no harmful gene changes were found in the tested genes.
  • A variant of uncertain significance (VUS): Means a change whose effect is not yet known, because there isn’t enough information available. (Over time, doctors may understand this change better, most of the time it turns out to be harmless, so it usually doesn’t affect medical decisions).
• Post-Test Counselling: The results are clearly explained to you, and based on them, your doctor discusses the next steps, such as regular screening, ways to reduce risk, or treatment options if needed⁹.

Note: Testing is usually recommended based on trusted medical guidelines.

When to Consult a Doctor?

If you observe any warning symptoms or have a family history that puts you at risk for cancer, you should contact a doctor. Early medical guidance can aid in immediate detection and better results.

Signs and Symptoms That Need Medical Attention

The following are some warning signs that you should not ignore and seek immediate medical attention for:

• Unexplained weight loss
• Constant fatigue or weakness
• Nausea, vomiting or lack of appetite
• Persistent pain that doesn’t go away
• A lump or thickening in any part of the body (such as breast or neck)
• Changes in skin, moles, or unusual bleeding
• A sore that doesn’t heal or yellowing or skin
• Persistent cough, hoarseness, or difficulty swallowing
• Changes in bowel or bladder habits
• Changes in mouth, such as soreness, bleeding, pain or numbness¹⁰

Family History and Risk-Related Situations

Family history might enhance your cancer risk and should not be ignored, especially if you are experiencing symptoms. Multiple family members with cancer, cancer at a younger age, the same type of disease returning in the family, having a close relative with cancer, or a family history of related cancers such as breast and ovarian cancer are all warning signals that should be discussed with a doctor⁹.

Along with consulting a doctor, opting for a comprehensive full-body checkup can help in early detection of potential health risks.

Conclusion

Cancer is a genetic disease however not all cancers are passed on. Understanding the difference between somatic and hereditary cancer might help you determine your risk and take appropriate action. Paying attention to family history and considering genetic testing as needed can help with early detection and treatment. Taking informed action now can result in improved health outcomes tomorrow.

Also Read: Types of Cancer: Symptoms, Early Signs, Diagnosis & More

Frequently Asked Questions (FAQs)

References

1. The Genetics of Cancer. 2024. doi: https://www.cancer.gov/about-cancer/causes-prevention/genetics
2. Risk Factors. 2025. doi: https://training.seer.cancer.gov/colorectal/risk-factors.html
3. Cancer risk in families. doi: https://cancer.ca/en/cancer-information/what-is-cancer/genes-and-cancer/cancer-risk-in-families
4. Gene Amplification. 2026. doi: https://www.genome.gov/genetics-glossary/Gene-Amplification
5. Genes, Tumor Suppressor. doi: https://www.ncbi.nlm.nih.gov/mesh?Cmd=DetailsSearch&Db=mesh&Term=%22Genes%2C+Tumor+Suppressor%22%5BMeSH+Terms%5D&utm
6. Can changes in the structure of chromosomes affect health and development? 2021. doi: https://medlineplus.gov/genetics/understanding/mutationsanddisorders/structuralchanges/
7. Cancer Genetics Risk Assessment and Counseling (PDQ®)–Health Professional Version. 2025. doi: https://www.cancer.gov/publications/pdq/information-summaries/genetics/risk-assessment-hp-pdq
8. Understanding Genetic Testing for Cancer Risk. 2025. doi: https://www.cancer.org/cancer/risk-prevention/genetics/genetic-testing-for-cancer-risk/understanding-genetic-testing-for-cancer.html
9. Genetic Testing for Inherited Cancer Risk. 2024. doi: https://www.cancer.gov/about-cancer/causes-prevention/genetics/genetic-testing-fact-sheet
10. Signs and Symptoms of Cancer. 2020. doi: https://www.cancer.org/cancer/diagnosis-staging/signs-and-symptoms-of-cancer.html
11. Chakraborty S, Rahman T. The difficulties in cancer treatment. ecancer. Published online 2012. doi: https://pmc.ncbi.nlm.nih.gov/articles/PMC4024849/

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