Cancer Runs in My Family — Should I Get Genetic Testing?

Finding out your mother or sister has cancer changes everything. Suddenly, you're not just thinking about their diagnosis — you're thinking about yourself. You're wondering if your genes might carry the same risk. You're scrolling at midnight, searching for answers that feel impossible to find.

If this is you, I want you to know: you're asking exactly the right question. The fact that you're here, looking for information, means you're taking control. And that's powerful.

Here's what I tell my patients: knowledge is not a sentence. It's a head start. Genetic testing for hereditary cancer risk doesn't tell you what will happen to you. But it can tell you what might, and that knowledge lets you make choices. Real, empowering choices about your health, your screening, your future.

Let me walk you through what hereditary cancer genetic testing is, what it can tell you, and how to figure out if it's right for you.

Not All Cancer Is Hereditary — But Some Is

Here's something important to understand right away: most cancer is not hereditary. About 85–90% of cancers happen by chance — they're sporadic. Your mom got breast cancer because of random mutations that happened during her lifetime, not because of genes passed down to her.

But about 5–10% of cancers are different. These are hereditary cancers, caused by inherited genetic mutations that run in families. If one of your parents has a hereditary cancer mutation, there's a 50% chance you inherited it too.

The difference matters. Knowing whether your family's cancer is hereditary completely changes what you do next.

The Most Common Hereditary Cancer Syndromes

BRCA1 and BRCA2 mutations are probably what you've heard about. These genes normally help protect you from cancer by repairing damaged DNA. When they're mutated, that protection is weakened. People with BRCA mutations have dramatically higher risks for breast cancer, ovarian cancer, and several others. This accounts for about 5–10% of breast cancers and 10–15% of ovarian cancers.

Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC) happens when genes that repair DNA are mutated. People with Lynch syndrome have very high risks for colorectal cancer and ovarian cancer. It accounts for 2–4% of all colorectal cancers.

Other syndromes exist too — familial adenomatous polyposis (FAP), Li-Fraumeni syndrome, hereditary diffuse gastric cancer — but they're rarer. Your genetic counselor will help you understand which ones might apply to your family.

Signs That Cancer in Your Family Might Be Hereditary

Not everyone with cancer in their family should get genetic testing. Testing makes the most sense if your family pattern suggests a hereditary mutation. Here are the signs:

• Multiple family members with the same cancer or related cancers (like breast and ovarian, or multiple colorectal cancers)
• Cancer diagnosed unusually young — especially before age 50. A 35-year-old with breast cancer is more likely to have a genetic mutation than a 70-year-old
• Ashkenazi Jewish ancestry — BRCA mutations are more common in this population, and genetic testing is often recommended even with less dramatic family history
• Triple-negative breast cancer — this specific type is more likely to be BRCA-related
• Male breast cancer — this is rare and often genetic. If a man in your family has had it, genetic testing for women in that family makes sense
• Multiple primary cancers in one person — the same person diagnosed with two different cancers suggests a hereditary mutation
• Rare cancers like ovarian or pancreatic cancer, especially in younger people

Do any of these sound like your family? If yes, genetic testing might be worth exploring.

But here's the thing: you don't have to have all of these. Even one strong sign — like a sister with breast cancer before age 45, or an aunt who had ovarian cancer — might be worth discussing with a genetic counselor.

What Genetic Testing Can Tell You — And What It Can't

Let's be really clear about what a genetic test result actually means, because this is where a lot of confusion happens.

A Positive Result

If you test positive for a hereditary cancer mutation (like BRCA1 or a Lynch syndrome gene), it means you carry that mutation. This increases your lifetime cancer risk. But — and this is crucial — it does not mean you will definitely get cancer.

For example, if you have a BRCA1 mutation, your lifetime risk of breast cancer is about 45–80%. That sounds high, but it also means some people with the mutation never get breast cancer. Many do live long, healthy lives with a positive genetic result — especially because they can do something about it. You're not helpless. You're informed.

A Negative Result

If you test negative for the mutations you were looking for, that's reassuring. Your cancer risk is much lower. But here's the nuance: if someone in your family carries a mutation and you test negative, you didn't inherit that specific mutation. Your risk is lower than if you were positive.

But you still have the same baseline cancer risk as everyone else. Genetic testing doesn't rule out sporadic cancer.

A VUS Result (Variant of Uncertain Significance)

Sometimes the test finds a change in your DNA that no one really understands yet. We call this a VUS. It might be important, or it might be harmless. The honest answer is: we don't know. These results are typically treated as negative (no special action needed), but your genetic counselor will explain what it means for you and monitor for new information that might clarify things.

What Testing Can't Tell You

Genetic testing doesn't predict your future with certainty. It doesn't tell you exactly when or if you'll get cancer. It doesn't tell you how severe any cancer would be. And it doesn't replace good health habits — diet, exercise, sleep, not smoking — which matter for everyone.

Think of genetic testing as adding one piece of crucial information to your health picture. It's not the whole picture, but it's an important piece.

What Happens During Hereditary Cancer Genetic Testing

Let me walk you through the process, because knowing what to expect helps ease some of the anxiety.

Step 1: Pre-Test Genetic Counseling

Before you even give a sample, you'll meet with a genetic counselor (or sometimes a doctor with genetics training). This is not a quick appointment — it's a real conversation. We talk about your family history. We explain what we're testing for and why. We discuss what the results might mean and how you'll feel about different outcomes.

This is your chance to ask questions. All of them. Nothing is too basic or too strange. A good genetic counselor wants you to feel informed and confident before you proceed.

Step 2: The Test Itself

The actual test is simple — usually just a saliva sample or a blood draw. You're looking at a couple minutes. We send it to a lab where highly trained technicians sequence your DNA, looking for mutations in the genes we discussed during counseling.

Step 3: Waiting

This is the hard part. Results usually take 2–4 weeks. (Sometimes longer, depending on the lab and complexity.) That waiting period is real, and it's okay if you feel anxious. Many people do. Some people find it helpful to journal, talk to a counselor, or lean on loved ones during this time.

Step 4: Results Consultation

You won't just get a report in the mail. You'll get a conversation. Your genetic counselor or doctor will sit down with you, explain your results, answer your questions, and help you understand what comes next. If you test positive, we talk about screening options, risk-reducing strategies, and family planning. If you test negative, we talk about your baseline cancer risk and good health practices.

This consultation is just as important as the test itself. It's where knowledge becomes action.

If You Test Positive: It's Not a Death Sentence — It's a Head Start

I want to address this directly, because when people test positive, fear is often the first emotion. And that's normal. But I've cared for hundreds of patients with positive genetic results, and I can tell you: a positive result is information. It's not a death sentence. It's a head start.

Enhanced Screening

If you have a BRCA mutation, for example, you'll likely get more aggressive breast cancer screening: MRI in addition to mammography, starting at age 25–30. For Lynch syndrome, you get colonoscopies every 1–2 years instead of every 10 years. These protocols catch cancers early, when they're most treatable.

Early detection matters. A cancer caught at stage 1 is a completely different scenario than stage 4.

Risk-Reducing Medications

For some hereditary cancers, medications like tamoxifen or aromatase inhibitors can reduce your cancer risk significantly. These aren't right for everyone, but they're an option worth discussing with your doctor.

Preventive Surgery

For some people with very high risks, preventive surgery is an option. Preventive mastectomy (removing healthy breast tissue) or preventive oophorectomy (removing ovaries) can dramatically reduce cancer risk. These are big decisions, and they're absolutely not right for everyone. But they're options. Real options that many people choose and feel good about.

Family Planning

If you're thinking about having children, knowing your genetic status is valuable information. Some people choose to use IVF with genetic testing (preimplantation genetic testing, or PGT) to avoid passing on the mutation. Others choose to have children who might inherit the mutation, knowing those children can be screened and monitored. Both are valid choices.

A positive result doesn't make parenthood off-limits. It makes it informed.

Why This Matters for Your Family Too

Here's something important that often surprises people: if you test positive for a hereditary cancer mutation, your family needs to know.

This is called cascade testing, and it's one of the most valuable things that happens after a positive result. If you carry a mutation, so might your siblings, your children, and sometimes your cousins and aunts and uncles. They have the same 50% chance you did of inheriting it.

And here's why that matters: your sister might not have any family history that would trigger genetic counseling on her own. She might not know to ask. But if you test positive, her doctor can then recommend testing for her, and she can make informed choices about screening, prevention, and her own family.

You're not just getting information for yourself. You might be changing the trajectory of health care for your whole family.

How to Talk to Your Family

This can feel uncomfortable, I know. You might worry about worrying them, or you might not know how to start the conversation. Here's what I usually suggest:

• Be matter-of-fact and positive. "I got genetic testing done, and I want to tell you about it so you can make your own choices."
• Explain what you learned, but don't oversell or catastrophize. "It means my cancer risk is higher, but I have a plan to screen and monitor."
• Invite, don't insist. "I think it might be worth you talking to a genetic counselor about whether testing makes sense for you too."
• Share resources. Give them information. Make it easy for them to take the next step if they want to.

Your siblings will likely be relieved. They probably wondered about this too. You're giving them the same gift you got: information, choices, and agency.

Frequently Asked Questions

Does genetic testing cost a lot?

Testing itself has become much more affordable in recent years — often just a few hundred dollars if you're paying out of pocket. Most insurance plans cover it if there's medical indication (like family history of cancer). We can help you understand your costs before you commit.

Will my genetic information be private?

Yes. Genetic information is protected by HIPAA, just like all your medical information. Your results are yours — we don't share them without your permission. The genetic testing lab stores your sample securely, and you can request that it be destroyed after testing.

What if I'm adopted or don't know my family history?

This is more nuanced. Without family history, we have less information to guide testing. But if you've been diagnosed with cancer yourself, genetic testing is often recommended regardless of family history (this is called genetic testing in the context of your own cancer, rather than family history). Talk to a genetic counselor about your specific situation.

Can I just do a direct-to-consumer genetic test from ancestry companies?

Those tests look at some genetic variations, but they're not designed for medical purposes. If hereditary cancer risk is a real concern for you, clinical genetic testing — done in a medical setting with counseling — is more thorough and meaningful. It's also more likely to be covered by insurance.

How often should I be screened if I have a hereditary cancer mutation?

It depends on which mutation you have and which cancers you're at risk for. BRCA mutations call for very frequent breast screening (often MRI every 6 months and mammography every 1-2 years, starting in your 20s). Lynch syndrome requires frequent colonoscopies. Your genetic counselor and oncologist will create a specific screening plan for you.

Can genetic testing detect all hereditary cancers?

Not all of them. We can test for the most common ones (BRCA1, BRCA2, Lynch syndrome genes, and others), but hereditary cancer is still an evolving field. New genes are discovered regularly. Your genetic counselor will explain what your specific test covers.