16 Signs of Canine Cancer You Need to Know

How to Prevent, Spot, Diagnose and Treat Cancer in Dogs

Dogs are endless sources of unconditional love; no one will ever be happier to see you come home than your loyal canine companion. So, if and when you hear the word “cancer” regarding your precious pet, there’s no denying how difficult a moment can be. Fortunately, the earlier we catch canine cancer, the better the prognosis. Because of that, we’ve rounded up some information that will help you know what to watch out for that will help you act swiftly in the case of canine cancer.

In the following article, we’ll share information on the following:

  • Signs and symptoms of cancer in dogs
  • The types of canine cancer
  • Steps you can take to prevent canine cancer
  • How your veterinarian can diagnose and treat cancer

Signs and Symptoms of Cancer in Dogs

Dogs can be somewhat stoic about pain but generally don’t hide it as much as their cat counterparts. And while the signs will depend on the dog and the type of cancer, there are some things you can look out for as a diligent pet owner.

Some signs and symptoms of canine cancer are:

How active is your dog? Are they experiencing abnormal weight loss?
  1. Sores that don’t heal
  2. Weight loss that doesn’t come from you altering your dog’s diet and exercise regimen, as this could indicate a tumor in the intestines, stomach, or elsewhere
  3. Abnormal masses that continue to grow—these should be examined to determine if they are cancerous
  4. Appetite loss
  5. Foul odors from the dog’s mouth, ears, or other body parts
  6. Difficulty eating or swallowing and subsequent appetite loss, as a lump can put pressure on the esophagus
  7. Bleeding or discharge from any opening
  8. Persistent lameness or stiffness, which could indicate bone cancer
  9. Wounds that don’t heal, particularly if the dog has been given antibiotics and they persist
  10. Exercise intolerance or lethargy
  11. Difficulty breathing due to a mass on the windpipe or lung
  12. Difficulty defecating due to a mass on the rectum or anus
  13. Difficulty urinating due to a mass on the bladder, prostate, or urethra
  14. Coughing
  15. Signs of pain
  16. Abdominal swelling

While the list of possible signs of cancer in your dog is long, there is no reason to worry excessively. We want to arm you with as much knowledge as possible so you can act quickly if you notice anything since early detection is paramount in treating canine cancer.

Types of Canine Cancer

You might recognize some types of cancer in dogs, as there is much crossover with the types we see in humans.

The most common types of cancer in dogs are:

  • Squamous Cell Carcinoma — Most commonly found on the dog’s toenail beds or in their mouths, surgery is often successful if caught early enough. However, it is often more aggressive when found in the tonsils or on the tongue.
  • Mouth and Nose Cancer — In the case of mouth cancer, you might notice an odor, trouble eating, bleeding, or a mass on the gums. With nose cancer, you might see your dog having difficulty breathing, bleeding from their nose, or having a swollen face. Early treatment for both is essential.
  • Melanoma — You might think this skin cancer would occur in dogs with light skin, but it’s actually the opposite—dark-skinned dogs are more prone to melanoma. You might notice small lumps or flat, wrinkled masses.
  • Mast Cell Tumors — Mast cells are found in all tissues of the dog’s body but form tumors in approximately 20 percent of the population. There’s quite a range in severity, with some being relatively benign and others being more aggressive.
  • Osteosarcoma — The most common form of bone cancer in dogs, osteosarcoma mainly affects large or giant breed dogs (though it can affect dogs of all sizes and ages). What you’d see would likely be lameness or swelling in the affected leg or area.
  • Soft Tissue Sarcoma — A slow-growing mass that can show up anywhere in the body, a soft tissue sarcoma can typically be treated with surgery to remove the tumor and sometimes radiation. Your veterinarian may need to choose a more aggressive treatment if the cancer has spread.
  • Lymphoma — Seen more often in Golden Retrievers, Standard Poodles, and Australian Shepherds, lymphoma is generally treatable when detected early. It’ll typically appear as swollen glands or lymph nodes behind the knee, under the neck, or in front of the shoulders. An impacted dog might have trouble with digestion and/or breathing.
  • Bladder Cancer — This is slow-growing cancer that will reveal itself in things like urinary obstruction and bleeding, but these signs might now show up for three to six months or so after the dog gets it.
  • Testicular — This form of canine cancer is common in dogs that are still intact and is largely preventable with neutering. It is also generally curable with surgery if caught early on.
  • Mammary — As with intact male dogs, mammary cancer is a higher risk for female dogs who have not been spayed. However, it can happen in any female dog, and your veterinarian will try to remove it with surgery if the cancer hasn’t spread.
  • Hemangiosarcoma — This type of cancer is more common in middle-aged to senior dogs and in Golden Retrievers and German Shepherds after they are older than about five. It is an incurable tumor of cells that often doesn’t present signs until the tumors are treatment resistant.
  • Brain Tumor — If your dog has a brain tumor, they’ll likely show behavior changes and/or have seizures. Your veterinarian will remove the tumor if it’s operable, which can be determined with a CAT scan or MRI.
  • Malignant Histiocytosis — Occurring most in large breed dogs, this cancer shows up as lesions on large limbs and joints or throughout the body.

Steps You Can Take to Reduce Your Dog’s Chances of Getting Cancer

As with humans, cancer can sometimes be a matter of genetics. However, there are lifestyle changes you can make to increase your dog’s chances of staying healthy and, ideally, avoiding a cancer diagnosis.

Some things you can do to try and prevent cancer in your dog are as follows:

Maintain an optimal weightObesity in pets is at epidemic proportions, and this excess weight has been linked to inflammatory reactions such as cancer. Two things you can do to combat obesity in your dog are helping them to get regular exercise and feeding them a healthy, balanced diet. If you’re unsure of the best way to accomplish either of those things, please don’t hesitate to reach out to your veterinarian. They’ll happily share the best ways to get your dog healthy ingredients and the right amount of exercise for their age and breed.

Avoid smoking in your environment — As everyone knows by now, smoking is a health hazard, but many don’t realize that humans and pets around those who smoke can fall victim to secondhand and third-hand smoke. ­­Although dogs rarely get lung cancer, some studies have shown that smoke exposure can increase pets’ risk for nasal cancers such as sarcomas and carcinomas. And thirdhand smoke is what lingers in things like toys, food, water, and even on a dog’s fur.

Ask your veterinarian about the likelihood of cancer in your dog’s breed.

Do your due diligence on your dog’s breed — As mentioned above, certain dog breeds are linked to an increased chance of getting types of cancers, so you might want to talk to your veterinarian about any predisposition your dog has and get extra screenings in those cases.

Minimize your dog’s exposure to chemicals — We know chemicals are all around us, but we can work to reduce our exposure. If your lawn company can’t ensure their treatment is safe for your pet, you might want to avoid that altogether. Certain cancers, such as lymphoma, have been linked to these environmental factors.

Don’t skip those annual wellness exams — You might think your dog seems fine, so why bother to go to your yearly exam for your dog? The reason you should is that the physical exam, along with urinalysis and blood/lab work, can detect issues that you might not have noticed. Catching cancer early is the best way to combat it.

Avoid allowing your dog too much time in the sun — Nearly all dogs love being outside. In fact, getting them back into the house can be quite the game of tug-of-war! While we’re not advocating that you keep your dog indoors, limiting the number of hours you’re outside is best to avoid sun-induced carcinomas.

How a Veterinarian Diagnoses and Treats Canine Cancer

In addition to examining your dog from nose to tail, your veterinarian has various tools in their toolbox to test for cancer if your dog is displaying symptoms. And then, depending on what they find, they’ll devise a treatment plan that ideally works for you, the dog, and the veterinary team.

The steps veterinarians will generally take to diagnose and treat cancer in dogs are as follows:

Testing to arrive at and confirm the diagnosis — Veterinarians will enlist any of the following to test for cancer in your dog: biopsy, blood/lab work, ultrasound, and needle aspiration.

The staging of cancer — Another crossover between the human and pet world, cancer needs to be “staged.” The veterinarian will use the test results to decide if the cancer is localized or has metastasized (spread). If they cannot do this based on the initial results, they may need to order further tests, such as an MRI or a CT scan. This staging process helps them know how to proceed with caring for your precious pet.

Seek out the expertise of a board-certifed oncologist, and we’ll work them to treat your dog!

Referral to a board-certified veterinary oncologist — While your veterinarian can help you far into the process, once cancer is staged, it’s sometimes best to get a referral to an oncologist. This PetCureOncology.com article notes, “Veterinary oncologists have specialized training and the latest information about new advances and treatment options.” That person will team up with your veterinarian throughout the course of your dog’s treatment.

The oncologist will create a customized treatment plan. Depending on the type of cancer and the stage, your dog’s oncologist will likely choose from one of the following treatment options: chemotherapy, immunotherapy, surgery for tumor removal, radiation, and other developing therapies.

Treatment and checkups will begin — Once the treatment plan is in place and you are on board with it, your veterinarian and oncologist will work together to start the treatments and order checkups to ensure all is going smoothly.


If you’ve recently been told your faithful canine companion has cancer, or you suspect it based on some recent symptoms, we know you’re likely worried. The best thing to do is to err on the side of caution and see your veterinarian get a plan in place to either confirm, cure or, hopefully, at least add years to your precious pet’s life.

Do you have further questions about canine cancer, or would you like to make an appointment? Contact us today!