signs of canine cancer

Warning Signs Of Cancer In Dogs

Approximately one in every four dogs will develop neoplasia at some point in their lives. Knowing the warning signs of cancer in dogs are crucial.

Unfortunately, though the cause of most canine cancers is unknown, there are things you can do to help keep your dog healthy. Today, dogs are living longer thanks to better treatment, more advanced technologies, modern testing, and diligent pet parents.

There are many different types of cancer in dogs and the outward signs may not always be obvious nor present themselves at all. I know because I lost my beloved Cocker Spaniel, Dexter, to canine hemangiosarcoma. He was fine and happy with a clean bill of health one moment and gone within 24 hours.

If you are interested in how to know if a dog has cancer, stick around. We’ll be sharing stories from dog moms who dealt with cancer cancer, how they discovered, what they did, and how their experiences can help you and your dog.

Common Signs of Cancer in Dogs

You cannot tell what a lump is by looking at it nor by palpating it. Even the most qualified specialist can speculate, but there is no 100 percent certainty without further testing.

Common Signs of Cancer in Dogs include:

  • Appearance of a lump or bump on or under the skin or discoloration
  • Foul odors from the mouth, nose, anal regions, or any other body part
  • Abnormal or sudden discharge such as blood, vomiting, diarrhea, or pus
  • Wounds that are slow to heal or do not heal
  • Sudden weight loss for dogs not overly active nor on a diet
  • Changes in appetite and/or difficulty swallowing
  • Difficulty breathing or coughing
  • Decreased energy or lethargy
  • Changes in urination or defecation (i.e., straining, frequency, blood, foul odor, etc.)
  • Evidence of pain
  • Abdominal swelling (distended) or sudden weight gain
  • Unexplained heat, pain, lameness, or swelling
  • Mouth/oral changes
  • Nosebleeds
  • Seizures

This is by no means an all-encompassing list, but these represent the most common signs of canine cancer.

Common Canine Cancers include:

  1. Hemangiosarcoma
  2. Mast cell tumors
  3. Lymphoma
  4. Osteosarcoma (bone cancer)
  5. Brain tumors
  6. Bladder cancer
  7. Mammary carcinoma
  8. Malignant histiocystosis
  9. Squamous cell carcinomas
  10. Mouth and nasal cancer
  11. Melanoma
  12. Testicular cancer
  13. Fibrosarcoma

As you see, dogs often the same cancers that affect humans, often with similar symptoms. Since dogs can’t tell us when something feels ‘off,’ knowing the signs of canine cancer may save your dog’s life.

Signs of Dog Cancer That You Should Never Ignore

When dog mom Sue Greenberg noticed a lump on her Cocker Spaniel, she took action. It all started when Marley sat down and the lump appeared. He stood up and it disappeared. Greenberg first saw the lump after taking a photo of her dog.

“Marley was being Marley, and nothing was out of the ordinary,” his mom shared. “This thing ate at me, though. I had a gnawing sick feeling inside.”

The devoted dog mom takes a lot of photos of her pups. Marley normally sits tall, but she noticed her regal boy hunching over in one particular photo. She ran her fingers over Marley, tried to palpate for anything out of the ordinary, but things seemed okay. Joel Greenberg, Susan’s husband, felt maybe it was the angle of the photo or because Marley was getting thin.

The couple was concerned about Marley’s weight and wondered if his thyroid may be out of balance. A thyroid test in early July after a slightly decreased weight was normal. A complete blood panel (CBC) performed at the request of the emergency veterinarian, was normal.

dog cancer symptoms
The lump is seen in this photo.

Days later, Greenberg placed a snood over Marley’s ears to prepare for meal time, when she saw a bulge. When the dog stood, it was gone. When he sat, again it was palpable.

Thinking it might be a fatty lipoma, she wanted a vet to see this. Since her last Cocker, Puddles, succumbed to hemangiosarcoma, her heart was hopeful but understandably nervous.

She made an appointment for when her vet returned from vacation, August 27th. She says that if it the mass was visible or felt while standing or laying down, the would not have waited to see the vet. As it turns out, they could not wait any longer, so they went to the emergency vet three days later.

“Once you have a dog touched by cancer, it sits in the back of your mind,” she shared.

Long time readers of this blog know that we believe in the ‘don’t wait, aspirate’ rule of thumb when it comes to lumps on dogs. At the very least, a veterinary visit is in order for further testing.

This seemingly innocuous lump turned out to be a very aggressive, high-grade form of cancer.

How Veterinarians Diagnosed Cancer in Marley

At the animal hospital, Marley was seen for a right flank mass diagnosed four weeks earlier, but which had sudden growth recently. The vet was able to palpate a small mass in the right lumbar area near the dog’s 13th rib. They could not define the mass but suspected a possible lipoma, or a fatty non-benign mass that affects many dogs.

The couple was told a CT scan could be performed, but they are expensive and though not necessarily needed, they could proceed forward with it. The couple was about to agree, but Susan noticed her husband seemed uncomfortable about that decision. The only way they could stop worrying was to go ahead with the scan.

“I got the call mid-afternoon from the surgeon to tell me Marley had cancer, that it had metastasized, and it was in his lungs,” the devastated dog mom shared. “He was completely shocked by the results and was grateful that Joel and I insisted on the CT Scan.”

More specifically, Marley’s CT scan of his chest and abdomen showed:

  • Numerous pulmonary nodules, most consistent with pulmonary metastatic neoplasia.
  • Soft tissue mass with primary concern for neoplasia, such as soft tissue sarcoma. The report says, “This mass appears to deflect into the abdomen rather than directly extending into it, although focal extension cannot be entirely excluded.”

A definitive diagnosis could be obtained through a biopsy/aspiration of the mass, but the Greenbergs were told Marley’s life span with treatment would not hopeful.

Dr. Julius Liptak, small animal surgeon and ACVS Founding Fellow in Surgical Oncology, wrote to the Greenbergs on a Friday:

I am so sorry to be the bearer of such unexpected and bad news. As you can see from the CT report, Marley has a tumor affecting the subcutaneous tissues of his right body wall and this tumor has spread (or metastasized) to his lungs.

As you know from our discussions this morning and subsequent phone call, I would not have ever imagined this possibility based on my physical exam of Marley this morning.

Unfortunately, we are now in a palliative setting for Marley and I would not recommend surgery for Marley because of his lung metastasis. His lung metastasis will be the cause of his passing.

The clinical signs associated with lung metastasis can vary from systemic signs (lethargy, decreased appetite, weight loss [which you are already seeing], and decreased activity levels) to signs associated with his lungs (labored breathing, increased respiratory rate, and coughing [with or without blood]).

Palliative management options include lots of TLC (which I know you’ll lather on Marley!), pain killing drugs and symptomatic treatment when he starts to show clinical signs associated with his metastatic lung tumor, and chemotherapy.

There are various types of chemotherapy ranging from full-course cytotoxic chemotherapy to metronomic, anti-blood vessel growth chemotherapy.

These vary in their potential for side-effects, but may reduce the growth rate of his metastatic lesions and minimize the progression of further lesions in the future.

I would recommend a consult with our medical oncologist to discuss the options for Marley and what this would mean for you and Marley if you chose to proceed with some form of chemotherapy.

signs of dog cancer

Life Shattering Decisions

Due to the high grade and very aggressive nature of this cancer, the chemotherapy pill was not an option, since it would take months to start working. Marley was given two weeks to one month to live.

The couple was given a list of symptoms for which to be aware, and they decided to continue allowing him to live the best life possible without treatment.

They did seek a holistic veterinarian’s advice, but this path only lead to more upset and heartbreak. Marley succumbed to metastatic cancer later that year.

A Dog Mom’s Advice About Canine Cancer Warning Signs

In her own words, here’s Susan’s advice to other dog parents:

I want other dog parents to please be observant of your dog on how he or she looks, behaves and if you see anything new especially a lump or what looks like slight swelling, please take your dog to the vet. Have the lump investigated.

Do not assume it’s nothing. Have the lump analyzed. The only way you will know for sure is if you run tests, aspirate, ultrasound, CT scan, x-ray, etc.

Don’t stop testing until you know for sure what it is. Cancer is tricky sometimes and doesn’t always follow the norm, as in Marley’s case. His cancer fooled one of the very few oncologic surgeons in Canada.

dog cancer
L to R: Marley, Susan, Woody, and Joel Greenberg

Nothing different could have been done to prevent this. I was told this cancer probably started around the time or shortly before I saw that slight bump or hump on Marley’s back/ side.

Even when I felt it for the first time on or around August 8th and brought him, requested a CT scan, and if Dr. Liptak operated on him to take out the mass, the cancer still would have spread. Chemo would not have been able to start for two weeks after surgery and the cancer would be in his lungs already. This is a very nasty cancer.

If we didn’t do these things, Marley would have passed away without a diagnosis. We would wonder for the rest of our lives what happened, what did we miss? Now, we know.

Cancer Resources

If you have a dog who has recently been diagnosed with cancer, there are many resources available. According to the Drake Center, canine cancer is the leading cause of death for dogs 10 years of age and older. However, half of all cancer in dogs is treatable if it is arrested in its early stages.

Helpful Links and Financial Assistance

The Veterinary Cancer Society (VCS) is an online resource with information on clinical trials in the field of veterinary oncology. The listing includes a breakdown by university veterinary schools and other clinical trials.

Fetch A Cure provides a variety of resources from cancer terms to nutrition, financial resources, and more. According to their research, approximately one-third of all tumors in dogs are skin tumors, and up to twenty percent of those are mast cell tumors.

The most common location to find mast cell tumors is the skin, followed by the spleen, liver, and bone marrow. Approximately half of all skin tumors are found on the body, another forty percent on the limbs (most frequently the hind limbs), and the remainder on the head or neck. Approximately eleven percent occur in more than one location.

Whole Dog Journal reports that one in four dogs gets cancer, and half of all dogs over the age of 10 will die from it. That is startling, but a very harrowing and all-too-real part of being a pet parent.

The Morris Animal Foundation has been in existence for over 70 years, helping animals with their health. According to their website, at any given time, they have over 200 studies underway to address important health challenges, including the largest cancer-focused study on dogs.

Whole Dog Journal also outlines a very intense article on the various cancer treatments for dogs. From conventional to holistic, cancer treatment and it’s prevention, run the gamut.

Financially, cancer treatment can be expensive.

This dog mom has been an advocate for reputable pet health insurance for years. If you are not among the millions of pet health policy holders, then what? Here are some solutions to helping you afford your dog’s medical bill.

Which Dogs Get Cancer?

Any dog, any age, any breed, any lineage, any mutt can be affected by canine cancer. Here are a few links to various pet blogs featuring dogs who have faced cancer, present company included.

Not all cancer diagnoses are as grim as Marley’s, which is why dog parents must be diligent in what is ‘normal’ in their dog. When abnormal happens, you will know.

We stress the importance of 10 touches to save your dog’s life. We perform these touches regularly on our dog, and we know many dog parents whose dogs’ lives have been saved because of these touches.

Dog mom and foster superhero Naomi Lukaszewski of California fostered and fell in love with a dog who was diagnosed with Stage 1A lymphoma. Of note, Naomi has fostered over 130 Cocker Spaniels, so she knows a thing or two about dogs and illness.

“Waffles showed no signs of being ill,” she says.

Cocker Spaniel with lymphoma
Meet Waffles.

Each week in our Club Cocker Facebook group, we do a “Touch Me Tuesday,” where everyone touches their dog to check for abnormalities. On this particular Tuesday, Naomi felt a large lump her the dog’s jaw. Knowing it was not there the night before, she acted.

A veterinarian made the diagnosis. Naomi had a dog with lymphoma before, and she knew the conventional treatment is chemo or prednisone.

“Once you choose prednisone, you cannot do chemo. The prognosis with chemo is 6-12 months including the 6 months of chemo. Prognosis on just prednisone is 2-4 months. The prognosis with no treatment is 1-3 months, she shared.”

Cancer and the Holistic Route

Having had two friends who recently went through chemo and finding out that the main difference between chemo for human versus dogs was that Waffles would not lose her hair, Naomi opted for prednisone to give Waffles the best quality of life she could have. She also decided to seek advice from a holistic vet, Dr. Katie Kanga of Integrative Veterinary Care.

Dr. Kangas provided her a list of supplements to support Waffles’ immune system and every visit includes acupuncture. This summer, they also did six weeks of ozone treatments.

She also discovered that vitamin D is a common deficiency in dogs with cancer. Not all dogs with vitamin D deficiency will get cancer, but dogs with cancer generally have a vitamin D deficiency. Dog parents, be warned: you should not immediately start supplementing with vitamin D.

There is a blood test for this, and if your regular vet does not perform it, then a qualified holistic vet can. Read more about dogs at risk from vitamin D deficiency.

Waffles continued to eat well, surprising her conventional veterinarian with her vitality.

“Her lymph nodes in her neck were like golf balls and she had horrible gingivitis (which really bugs me because I was so careful to brush her teeth daily),” Naomi told us. “While she has energy, she does not have stamina.”

She has lost muscle tone, her hair stopped growing, but none of her lymph nodes are swollen. Prior to getting into holistic treatment, Naomi felt it meant treatments to make her dying easier. She has since come to realize that her experience with holistic medicine has been giving her treatment to keep her healthy and extend Waffles’ life.

Naomi muses, “She still is sassy enough to ignore me when I tell her to stop barking.”

She cautions, however, that every dog is different and that you should always consult with a vet (conventional or holistic) before starting any type of medical treatment for your dog.

Update: Waffles passed away in October of 2018. May she rest in peace.

Reducing Cancer Risks In Dogs

No one has a crystal ball, and sometimes even the healthiest people and dogs can be diagnosed with cancer. Every dog is different, just like people.

You can’t determine how your dog will respond to chemo or radiation or any other number of treatments, curative or palliative in intent, until you are deep into the throes of cancer. You can, however, increase the likelihood your dog won’t be affected by cancer with some simple preventative measures.

Try and limit the chemicals your dog is exposed to from second hand smoke to lawn treatments. Use more natural flea and tick treatments.

Keep your dog in good shape and don’t allow him to become overweight. Overweight and obese dogs are more likely to develop certain types of cancer.

We are advocates and believers in preventative medicine. From what your dog eats to what you put on his skin, his overall emotional well-being and how much exercise – both mentally and physically – he gets, we would rather spend more on keeping illness away than spending a ton on trying to solve a huge health crisis.

Dealing With Canine Cancer

Never let anyone tell you what is best for you and your family. Marley is one of millions of dogs affected by cancer every year. It is evil, unforgiving, ruthless, and the best we can do for our beloved dogs is give them our best: commit to good health, diet, exercise, avoid chemicals, see the veterinarian regularly, and spend time together.

Life is short, and life is unexpected. Make no apologies for living life with dogs and how you treat them. If you want to ride a boat and eat ice cream together, go for it. If you are a hiker and love to explore new territories, don’t wait. Make a do it now list and don’t want for that bucket list.

Dog Cancer Resources

In our many years of blogging, we’ve encountered countless numbers of pet bloggers, presently company included, whose dogs have been affected by canine cancer. Here are a few of their journeys for further reading (the links will take you right to their pages dedicated to canine cancer):

Dr. Sue Cancer Vet YouTube Channel

Hemangiosarcoma in Dogs: My Dog Died Without Warning

Some Pets: Canine Lymphoma Resources

Long Haul Trekkers Sora’s Cancer Story

Help For Dogs With Mast Cell Tumors

Facebook: The Dog Cancer Series

Special thanks to Susan and Joel Greenberg and Naomi Lukaszewski for sharing their stories and to Dr. Julius Liptak, VCA Canada, Alta Vista Animal Hospital, for your expertise. Always check with your dog’s veterinarians and healthcare team before making any changes, deletions, or additions, to your dog’s diet and/or medicinal supplements. We cannot guarantee anything and no two dogs are alike. 

Dog cancer warning signs


  1. this article touched me so much because my Evie passed away a yr ago aug. from histiocytic sarcoma. she had a tiny little bump b/t her toes, which had been removed by a former vet when she was a few yrs old. i fought with the vet abt removing it and doing more, she refused, my fault, i should have gone to another vet. it came back when Evie was about 15. it was barely noticeable. it would be there one day and not for several days. too late. Evie fought a long hard battle, doing chemo, supplements, for almost a yr. the vets said she had such a strong will to live that she fought hard. the cancer vet had resources to try things that other drs did not have in my area. i was willing to travel anywhere. he tried 4 types of chemo and 1 new drug. she could not go under anesthesia for radiation b/c of her age and other health problems. the vets thought she would live another 6 mos or more but it got into her throat and lungs. none of the chemo would work, even though the major mass in her chest had died, it sprouted like babies in other parts of her body. my reg vet removed 2 lumps on her side, without chemo. she was a trouper. i blame myself for not doing more when she was younger and taking her to another vet. i blame myself for not taking her immediately to the vet when i noticed the little bump that kept disappearing. she had a stroke while i was feeding her, i gave her cpr and rushed to the cancer vet’s er, the vet on call wanted to put her down but i said not, put her in oxygen tent til her dr came in the am, i waited all nite, when he came in he work me up and said it was time. we had just seen him the day of this. he said he did not see this happening. everyone at this vet’s office loved Evie because she was the best patient, and so cute. i held her for hours, i did not want to let her go. now with my 2 other girls, the least little bump i rush to the vet. i dont care abt the cost. my vet knows that she needs to check out every little bump. it does not bother her because she knows that i am worried abt cancer again. thank you for the information.

  2. I found a lump under my dog’s collar recently when I took it off for her weekly bath. It turned out to be a soft tissue sarcoma. Thankfully, her chest & abdominal x-rays are clear of mets. And the surgeon got good margins.

    I found it about 6 weeks before her annual wellness visit & I am very grateful that I took her in instead of waiting for her regular exam! Now, she has been cleared of cancer.

  3. Sister and I recently lost our 10 year old Cocker to lung cancer. Sampson ate, played, did his business as usual close to the end. What got my sister to take him to the vet was he began sitting with his head out between the porch railing for shorter periods of time, leaning more to one side than maintaining his erect posture, becoming withdrawn from his family. His annual check – up went well but a visit 4 months later confirmed the worst. X – rays showed some spotting on a lung. Vet gave medication, said return in 2 weeks. If spots are there he has an aggressive form of lung cancer and 6 – 8 weeks to live. What we learned lung cancer is being diagnosed more frequently and found primarily in dogs 10 or older. The vet was right. We sent Sampson to a safe place at 6 1/2 weeks.

  4. As always, fantastic information and detail that is so helpful to dog parents. I hope Marley continues to live his best life as long as possible – I would have made the same choice. The C word scares me to death. Icy went to the vet recently and has a slightly high white bloog cell count. He suspected some type of parasite, even though the stool sample was negative for parasites. He’s told us to return in a month. She seems fine but I still worry. Thanks for sharing.

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