*Quick note: This blog is for educational purposes only and is not a substitute for veterinary care. Always talk to your vet about your dog’s specific situation.
*As you read this blog please remember there are treatments out there. The goal of this blog is to help you know what to look for and how to help your pup.
If you’re reading this, chances are you love a dog so much it makes your chest ache a little. Who am I kidding? It doesn’t just ache, it’s overwhelming.
Many of you know I started Three Yellow Dogs to honor our three beloved pups: Riley, Penny, and Winston. All three have now crossed the rainbow bridge. A lot of the time, I write light-hearted, helpful blogs because it’s easier to stay on the fun side of things.
But the truth is, even though Riley, Penny, and Winston have been gone for years, it still hurts to think about losing them. I’m sure it always will.
Even so, I feel strongly about sharing what we’ve learned in hopes that it helps other dog parents spot the early signs of canine cancer and feel a little less alone if they ever face it.
I remember, as clearly as if it were yesterday, the vet visit when we found out our sweet Penny had cancer. I asked our vet, “Do all dogs end up getting cancer if they live long enough?” I wish I could remember her exact answer, but I later learned that many sources estimate about half of dogs over the age of 10 will develop cancer.
So when we talk about canine cancer, we’re not speaking from a business standpoint. We’re talking as dog parents who have twisted a leash in our hands in that exam room waiting for news, and then cried for days on end. I’ve said it before and I’ll say it again: this is personal.
This blog is here to give you simple, honest information. We’ll go over:
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What cancer is
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Why it happens
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How to try to prevent it
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Signs and symptoms to watch for
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Questions to ask your vet
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How to help your dog if cancer enters your world
Grab your notepad (and maybe some tissues), and let’s dive in.
What Is Canine Cancer, Really?
In simple terms, cancer happens when some of the body’s cells stop following the rules.
Normally, cells grow, do their jobs, and then quietly retire. Cancer cells don’t retire. They ignore the “stop” signals and keep dividing when they shouldn’t. Over time, these abnormal cells crowd out healthy cells and interfere with the body’s ability to do what it needs to do to stay strong and well.
These misbehaving cells can:
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Form lumps or tumors
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Invade nearby tissues
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Spread to other parts of the body
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Interfere with normal, healthy functions
Some cancers grow slowly and can be removed or managed. Others are aggressive and progress quickly.
The Top 5 Most Common Cancers in Dogs
Different studies list things slightly differently, but most veterinary cancer groups agree that these are among the most common cancers in dogs:
1. Lymphoma
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Cancer of the lymph nodes and lymphatic system
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Often shows up first as enlarged lymph nodes (like a firm lump under the jaw or behind the knees)
2. Mast Cell Tumors
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The most common malignant skin tumor in dogs
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Often appear as new or changing skin lumps or bumps
3. Osteosarcoma (Bone Cancer)
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The most common primary bone tumor in dogs
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Especially seen in large and giant breeds; often causes sudden lameness or bone pain
4. Hemangiosarcoma
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An aggressive cancer of blood vessel cells
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Commonly affects the spleen, liver, or heart and can cause sudden internal bleeding or collapse
5. Melanoma
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A tumor of pigment-producing cells
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Often found in the mouth, on the gums, or on the toes, and can spread quickly
Why Do Dogs Get Cancer?
This is one of the hardest questions to answer, and often there isn’t one simple explanation. Here are some of the most common factors:
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Age: As dogs get older, their cells have had more time to accumulate tiny mistakes.
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Genetics: Some breeds and family lines are more prone to certain cancers.
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Environment: Long-term exposure to things like second-hand smoke, certain chemicals, or too much sun can increase risk.
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Random chance: Sometimes, even with the best care, cancer happens for reasons we simply can’t control.
Are Some Breeds More Prone to Cancer?
Unfortunately, yes, some breeds do seem to have a higher risk of cancer. This doesn’t mean these dogs will definitely get cancer, but it does mean we should be extra on top of checkups and early signs.
Breeds often reported to have higher cancer risk include:
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Golden Retrievers
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Flat-Coated Retrievers
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Bernese Mountain Dogs
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Rottweilers
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Boxers
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Labrador Retrievers
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Scottish Terriers
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Doberman Pinschers
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Great Danes and other large or giant breed dogs
But here’s the most important part:
Any dog, purebred or mixed breed, tiny or giant, can get cancer, especially as they age.
If your dog is one of these higher-risk breeds (or a senior pup of any kind), consider:
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Twice-yearly vet visits instead of once a year
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Asking your vet about baseline bloodwork and occasional imaging
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Doing regular “nose-to-tail” home checks for new lumps, bumps, or behavior changes
Can You Prevent Cancer in Dogs?
Unfortunately, there’s no guaranteed way to prevent cancer. But you can lower risk and improve your dog’s odds of staying healthier longer. Here are a few ways to help prolong your dog’s life:
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Keep a healthy weight. Obesity is linked with many health problems, including some cancers.
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Feed a balanced, high-quality diet. Good nutrition supports the immune system and overall health.
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Regular vet checkups. Yearly (or twice-yearly for seniors) exams help catch changes early.
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Spay/neuter when appropriate. This can reduce the risk of certain reproductive cancers.
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Limit toxins. Avoid second-hand smoke, minimize harsh chemicals in the yard and home when possible, and use pet-safe products.
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Sun protection for light-coated dogs. Limit intense sun exposure and ask your vet about protection for noses and ears if needed.
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Do regular grooming and hygiene. Regular grooming can help you spot lumps, bumps, and anything out of the ordinary.
Prevention isn’t perfect, but early detection plus a generally healthy lifestyle can make a big difference.
Common Signs of Cancer in Dogs
Dogs are champions at pretending everything is fine. That’s why small changes can be big clues. None of these signs automatically mean “cancer”—they can be caused by many different issues—but they do mean: call your vet.
1. New or Changing Lumps
Dogs get a lot of lumps and bumps, so don’t freak out when you see or feel one—but do get it checked out. Staying vigilant is key. If the lump is 1cm or larger, go to the vet and get it checked out.
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A new bump under the skin
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A lump that’s growing, changing shape, or feels very firm
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A lump that bleeds, oozes, or doesn’t heal
2. Weight Loss & Appetite Changes
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Losing weight even though they’re eating the same
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Suddenly not wanting to eat, or only picking at food
3. Low Energy or “Just Not Themselves”
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Less excited about walks, toys, or greeting you
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Sleeping much more than usual
4. Bathroom Changes
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Straining to pee, peeing small amounts often, or blood in the urine
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Vomiting or diarrhea that lasts more than a few days
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Black, tarry stool (can be a sign of internal bleeding)
5. Breathing & Coughing
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A cough that doesn’t go away
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Panting at rest or seeming short of breath
6. Pain, Limping, or Stiffness
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Limping for more than a couple of days
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Not wanting to jump on the couch or into the car
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Whining, hiding, or flinching when touched
Quick Reference: When to Call Your Vet
Call your vet soon if you notice:
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A new lump or bump, or one that’s changing, growing, or not healing
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Unexplained weight loss or a big change in appetite
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Low energy or your dog just “not acting like themselves”
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Ongoing vomiting or diarrhea (more than a few days)
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Changes in peeing or pooping, especially straining or blood
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A cough that doesn’t go away or trouble breathing
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Limping, stiffness, or signs of pain that last more than a couple of days
You know your dog better than anyone. If something feels off and doesn’t get better, it’s always okay to call your vet and ask.
How Vets Check for Cancer
You don’t have to diagnose anything at home—in fact, you shouldn’t. Your job is to notice. Your vet’s job is to figure it out.
If your vet is concerned about cancer, here’s what might happen:
1. Exam & Questions
They’ll:
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Feel your dog all over
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Check lymph nodes
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Listen to the heart and lungs
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Ask about behavior, appetite, bathroom habits, and any changes you’ve noticed
2. Basic Tests
These may include:
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Bloodwork
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Urine tests
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X-rays
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Ultrasound
3. Looking at Cells
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A tiny needle sample from a lump (fine needle aspirate)
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Or a small piece of tissue (biopsy)
4. Staging (How Far It’s Spread)
If it is cancer, your vet may suggest more imaging or tests to see:
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Where it is in the body
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Whether it has spread to other organs
It all sounds scary, but each step helps answer the big questions:
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What is this?
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Can we remove it?
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Can we slow it down?
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How do we keep my dog comfortable?
Treatment Options (In Plain Dog-Parent Language)
Every dog, every family, and every budget is different. There is no one “right” path. Here are the main tools vets and veterinary oncologists use:
1. Surgery
If the cancer is mostly in one place, surgery may:
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Remove it completely
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Or remove most of it to help your dog feel better and slow things down
2. Chemotherapy
Chemo for dogs is not exactly like chemo for people.
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Vets usually use lower doses so dogs can still feel good during treatment.
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Many dogs keep playing, eating, and enjoying life while on chemo.
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Side effects (like vomiting, diarrhea, or low white blood cell counts) can happen but are often temporary and manageable.
Chemo is commonly used for:
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Lymphoma
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Some mast cell tumors
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Certain bone or organ cancers
It may be used alone or after surgery.
3. Radiation Therapy
Radiation uses a very focused beam on one area. It’s often used for:
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Tumors in tricky spots (nose, mouth, brain, bones)
This usually requires a specialty hospital.
4. Targeted & Newer Therapies
Some cancers respond to:
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Medications that target tumor cells more precisely
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Treatments that help the immune system recognize and fight cancer
Your vet or oncologist can tell you if any of these options apply to your dog’s specific cancer.
5. Palliative (Comfort) Care
Sometimes the kindest choice is to focus on comfort rather than trying to cure the cancer.
Comfort care can include:
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Pain medications
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Anti-nausea drugs
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Appetite boosters
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Steroids to reduce inflammation
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Extra snuggles, soft beds, gentle walks, car rides, and cheeseburgers
Choosing comfort care is still choosing love.
Prognosis: What Does the Future Look Like?
We all want to know, “How long?” But dogs don’t read the charts, and they don’t count days—they live in moments.
Outcomes depend on:
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The type of cancer
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How early it was found
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Where it is in the body
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Your dog’s age and other health issues
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Which treatments you choose
Some cancers, when found early and removed, may barely change a dog’s lifespan. Others are more serious and may give us months instead of years.
Questions to Ask Your Vet
If you’re facing a possible cancer diagnosis, it can help to come in with a list. Here are some questions you might ask:
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What type of cancer is this?
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Has it spread, or do we need more tests to find out?
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What treatment options do we have?
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What are the goals of each option (cure, control, comfort)?
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What side effects should I watch for at home?
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How will treatment affect my dog’s daily life?
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What would you do if this were your dog?
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How can we keep their quality of life as high as possible?
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How will we know if our plan is working or needs to change?
Bring a notebook, a friend, or ask if you can record the conversation. It’s a lot to process when your heart is pounding.
*Screenshot or print this list and bring it with you. Add your own questions, too.*
How to Help Your Dog Day-to-Day
Whether you’re in the middle of treatment or focusing on comfort care, here are some ways to support your pup:
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Stick to routines. Familiar schedules can be calming.
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Offer tasty, vet-approved foods. Warmed-up meals, toppers, or softer textures can help picky eaters.
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Make moving easier. Ramps, rugs, and supportive harnesses can help with stiffness or weakness.
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Create cozy rest spots. Soft beds in warm, quiet places where they can still see their family.
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Watch for pain. Limping, panting at rest, restlessness, or withdrawal can all be signs. Tell your vet what you see.
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Celebrate the small wins. A good meal, a wag, a short walk, these are big victories on hard days.
Most of all, be present. Your voice, your smell, and your touch are their favorite medicines.
This is such a difficult topic. It’s a lot to take in, especially when your heart is already hurting and all you want is for your dog to feel better and stay with you just a little bit longer. I’ve tried to share as much information as possible without overwhelming you, but the truth is: it is a lot. And that’s okay. You don’t have to remember every detail. Just know that you’re doing your best by being here, learning, and loving your dog through all of it.
The million-dollar question will forever be: why don’t dogs live longer? Gosh, I wish I knew. I wish we could put our beloved fur babies in an invisible bubble that would prolong their lives and keep them with us forever.
I wish I knew how to keep my dog from getting cancer. The truth is, I don’t. My beloved Three Yellow Dogs all lived into their teens, but they all ultimately died from cancer. All I can say is that if your pup is going through cancer right now, we’re sending you the biggest, warmest hug. You are not alone in this. We are here for you. 💛🐾
For more detailed information please ask your vet and do your own research, there is tons of information out there. Here are a few helpful websites that can get you started:
https://www.fda.gov/consumers/consumer-updates/my-dog-has-cancer-what-do-i-need-know?
https://www.avma.org/resources/pet-owners/petcare/cancer-pets?
