Skip to main content

These 4 seemingly normal symptoms may mean your dog has cancer

No one wants to hear the C-word when it comes to your dog, but unfortunately, it’s a part of life. According to the American Veterinary Medical Association, about half of dogs over the age of 10 develop some form of canine cancer, though many of these pups enjoy many more years of health and happiness thanks to hardworking veterinarians and vigilant owners. So don’t panic—there’s a lot you can learn and do!

Keeping your fur baby healthy begins with understanding what their “normal” looks like. This way, you’ll be able to tell as soon as something seems off. Cancer symptoms in dogs can appear quickly, gradually, and in a number of ways, so knowledge will be your best friend when it comes to your pet’s health. You can start here, where we’ll go over a few cancer symptoms in dogs that might look normal on the surface.

Can dogs get cancer?

Unfortunately, dogs can get cancer just like people. In fact, reports the AVMA, dogs contract cancer at about the same rate as humans, though this rate goes up as a dog ages. Also like humans, not all cancers are cause for panic—many can be effectively treated or even left as-is. Still, you should keep an eye out for any odd symptoms, as these could be warning signs that your dog is battling cancer.

Weight loss

Weight can fluctuate from day to day, whether you’re human or canine, but large, sudden, or unexplained weight loss can be worth investigation. Of course, there are a few situations when you might expect a lighter dog—after a life-changing trip to the groomer or after having puppies, for example—but if this doesn’t apply, you may want to give your vet a call.

The issue may be as minor as a food allergy, so canine weight loss isn’t always a cause for concern. Still, it’s important to address this change because the cause can also be something more major. Weight loss or nutritional malabsorption may not be the root problem, but it can be a symptom of a number of illnesses and cancers. It’s better to be safe than sorry, don’t you think?

An English Cocker Spaniel rests in bed
Image used with permission by copyright holder


Behaviors and moods can change from moment to moment—that’s normal. So is a behavior change in response to something in the environment. But when you notice sudden, extreme, long-lasting, or unexplained lethargy, you should keep an eye on your pet.

Sometimes, lethargy can be the first sign of a medical condition that needs your attention. It could be minor, like when a dog has an upset stomach, or it could be a hint at something more complex. For example, if your old dog isn’t eating, you’ll need to look at the rest of their behavior before you know whether to be worried. As noted by Central California’s SPCA, other signs of lethargy include:

  • Lack of interest in food, water, and normal activity
  • Slower to respond to sensory stimulation, including your voice
  • Lack of energy or enthusiasm
  • Extreme tiredness
  • Restlessness

Lumps, bumps, and wounds

As your dog ages, lumps and bumps—including frequently-seen lipomas—will naturally develop under the skin. Don’t worry, though: Southern Arizona Veterinary Specialty & Emergency Center assures pet parents that these are not cause for alarm! They may grow into muscle tissue and need to be removed at some point, but your veterinarian will be able to keep an eye on anything before it reaches that point.

There are a number of other tumors that dogs can develop, especially during their older years. Merck Veterinary Manual notes that while some tumors are the typical lumps and bumps we think of, they “also can occur as hairless, discolored patches, rashes, or non-healing ulcers.” That’s why identifying skin conditions, wounds, and tumors should be left to a veterinary professional.

An Australian Shepherd mix rests on the couch
Image used with permission by copyright holder

Abnormal discharge or odors

Our four-legged friends are no stranger to body fluids, since they spend so much time licking themselves, but new or unusual discharge from anywhere in the body is worth a closer examination. Even the nose, which is usually wet, should not release excessive mucous (via Crown Veterinary Specialists & Associates). White, green, or yellow nasal discharge can be a sign of sinus infection or sinus cancer, as these kinds of illnesses are not common in healthy, vaccinated dogs.

Odd oozing from the mouth—whether blood, pus, or even excessive saliva—can also be a sign of oral cancers or infections. Stay vigilant for exceptionally bad breath, too; sudden stink can result from a number of these problems, notes Crown Veterinary.

You’ll also want to schedule a vet visit for any strange vaginal discharge in female dogs. Even though intact pups are much more likely to contract vulvar or vaginal cancer, it can occur in any canine (via The Veterinary Society of Surgical Oncology). Of course, genital discharge is supposed to happen at times in both male and female dogs, so don’t be afraid to ask your vet if you’re unsure.

Deep breath, pet parents—you can do this! Whether you’re doubling up on your knowledge or are concerned about your fur baby, you’re doing a great thing by researching cancer symptoms in dogs. The next step is to contact your veterinarian to confirm what’s going on. Even if it’s nothing, you’ll sleep soundly knowing you did what was best for your pup. That’s what being a dog owner is all about!

Editors' Recommendations

Gabrielle LaFrank
Gabrielle LaFrank has written for sites such as Psych2Go, Elite Daily, and, currently, PawTracks. When she's not writing, you…
Can dogs eat shrimp? The answer may surprise you
How to cook, cut, and prepare shrimp for dogs
A French bulldog puppy wearing a yellow sweater stands next to a dog bowl in front of a blue background

When dog owners are in the kitchen, it's only normal to have an extra pair of eyes watching their every move. Furry friends are never far away when food is around, and it's all too easy to toss your dog a table scrap their way when they look up with those pleading eyes. How could you say no?
Unless a dog is dealing with dietary restrictions or medical issues, the occasional bite of people food won't hurt. Of course, it's important to make sure that whatever you're feeding them is safe for canine consumption, as so many dog owners go to the internet to double-check. That's why you're here!
If you've been wondering, "Can dogs eat shrimp?" -- you've come to the right place. We'll break down everything you need to know about feeding dogs shrimp so you can get back to cooking.

Can dogs eat shrimp?

Read more
The best oversized dog beds your pup will love
One of these dog beds will help your puppers have a good night's sleep
Dog in bed with white blanket over his head

If you’ve ever come home from work and caught your pup snoozing on your bed, you know. Dogs like a soft place to lie down every bit as much as we do. And why not? They spend as much as 18 hours a day sleeping.

Big dogs, in particular, can develop health-related problems, such as arthritis, hip dysplasia, and joint pain, as they age. Not only does the right bed provide comfort and support, but it also enhances good sleep, which is equally important for their cognitive health. The right bed is also one that gives your pooch plenty of room to stretch out comfortably.
Our top recommendations
So, how big should a dog bed be? Take a look at these oversized dog beds for your favorite pup.
FurHaven Orthopedic Luxe Lounger

Read more
Does your dog drink a lot of water? Here’s when you should be concerned
It's usually just the weather, but you should look for signs of dehydration or excess thirst
A pug drinking water from a sink faucet

Ensuring your furry best friend gets plenty of water is one of the most important parts of being a pet parent. But how much water should your dog drink on a daily basis? Veterinarians claim the general rule of thumb is a simple equation: The majority of dogs require around 1/2 to 1 ounce (about 1/8 of a cup) of water per pound of body weight each day. Don't want to reach for your measuring cup? Make sure your pup has round-the-clock access to clean water, and everything should be fine.

That being said, if your dog empties their water bowl several times a day, or you notice their intake has increased drastically, you should probably keep a close eye on things. If your dog drinks a lot of water, you may be wondering, "Why is my dog always thirsty?" We'll share how to monitor your pup's water intake, the most common reasons your dog may be thirsty, and when you should speak with your vet.

Read more