The Earliest Signs of Cancer in Dogs That Most Pet Owners Miss, According to Vets
Let's be real for a moment: The word "cancer" is enough to send chills down anyone's spine. Unfortunately, cancer has affected so many of us, and it's a sadly common way to lose friends and loved ones—of the human and furry variety.
Cancer isn't always fatal, though. When it comes to cancer in dogs, veterinarians stress that noticing early signs can be life-saving.
"Just as it is in human beings, when a cancer is detected in an earlier stage, the cancer has a better chance of going into remission or being cured with surgery or medical treatment, such as chemotherapy or immunotherapy," says Jennifer S. Fryer, DVM, a veterinarian at Chewy.
Unfortunately, veterinarians share that there are commonly missed early signs of cancer in dogs to look out for. Here's what they want pet parents to know.
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At What Age Is Cancer Most Common in Dogs?
Generally, senior dogs are more likely to develop cancer than younger ones. According to the American Veterinary Medical Association (AVMA), about half of dogs over 10 will develop cancer. "As cells age, they are more likely to grow out of control or not die when they should," says Linda Simon, MVB MRCVS, a veterinarian with Senior Tail Waggers.
Still, a dog can develop cancer at any age.
Some cancers can occur in dogs of all ages, such as mast cell tumors and lymphoma," says Dr. Fryer. "Histiocytomas are benign tumors that occur almost exclusively in young dogs."
Can a Dog Have Cancer and Show No Signs?
Sometimes. "Early on in the disease process, signs may be subtle or non-existent," Dr. Simon says.
One example is splenic hemangiosarcoma.
"This is a cancer of the spleen, which can abruptly rupture and cause internal bleeding," Dr. Simon explains. "Before this happens, owners may not notice anything is amiss. In some cases, we may notice abdominal swelling, lethargy or pale gums."
Dr. Fryer says small, malignant tumors in the anal gland are also challenging to notice, and nearly half of them are found by surprise during wellness visits in pups without clinical signs.
"This is one reason why wellness exams for dogs are so important," Dr. Fryer says.
Related: The No. 1 Sign Your Dog's Poop Is Unhealthy
8 Commonly Missed Early Cancer Signs in Dogs, According to Veterinarians
1. A new lump, bump or lesion
Petting your dog is a sweet way to bond, but it can also clue you into whether your dog has new lumps or bumps—a cancer flag.
"Lumps and bumps on the skin or under the skin, especially those that grow rapidly or do not heal, could be indicative of early-stage cancer," says Nicole Savageau, VMD, a veterinarian with The Vets.
Dr. Fryer adds that lumps and bumps that go away or get smaller and return are also essential to look into.
Any new lump or bump that is not going away, growing larger, gets smaller and then comes back, or that sometimes bleeds should be investigated by a vet.
"While some bumps may be benign...there is no way to tell without looking at the lump’s cells under the microscope," Dr. Fryer explains.
2. Abnormal odors
Some pups can get a bit smelly between baths or after a particularly rowdy outdoor play session. However, a strange smell can also be a cause for pause (and a vet trip).
"Foul or unusual odors coming from the dog's mouth, ears or any other part of the body could be a sign of cancer," Dr. Savageau says.
3. Weight loss
Dr. Simon says pet parents may chalk weight loss up to old age. But unless the dog was on a diet, weight loss isn't normal.
"There can be many causes of weight loss, but unexplained weight loss in a dog whose appetite is the same and who does not have vomiting or diarrhea could be due to cancer," Dr. Simon says.
There's a reason weight loss is a potential cancer symptom.
"Cancer cells need a lot of energy to grow," Dr. Fryer says. "Some dogs with cancer may still be eating normal amounts, yet the bones of their spine are easier to feel, and their bellies are more tucked than they used to be."
4. Changes in bathroom habits
Something could be amiss if your once-regular pup is having trouble using the potty.
"Difficulty or pain during urination or defecation could indicate tumors in the urinary or gastrointestinal systems," Dr. Savageau says.
Dr. Fryer stresses that this issue is not exclusive to cancer, so don't panic, but do call the vet.
"Even if your dog seems to feel absolutely fine, and these signs are mild, it is worth a vet check," Dr. Fryer says.
5. Bleeding
Dr. Simon says pet parents may mistake vaginal bleeding for an unspayed dog's period or think a nosebleed is because of the weather. Her advice? Confirm it with your vet.
"Ongoing bleeding or discharge can be due to cancer," Dr. Simon says. "For example, bleeding from the vagina could indicate a uterine infection while nasal bleeding may be a sign of a tumor within the nose."
6. Lethargy or loss of energy
Some dogs have off days or might be less playful and active as they age. However, sudden or chronic energy level changes could be symptomatic of something more severe.
"If your dog is unusually tired and lacks energy, it could be a sign of an underlying health problem, including cancer," Dr. Savageau says.
Dr. Fryer concurs.
"If your dog is acting more tired lately, not wanting to go as far on a walk or isn’t finishing his or her bowl of food, but still seems normal in every other way, it is alright to monitor them for two to three days," Dr. Fryer says.
However, Dr. Fryer advises pet parents to call a vet if the issue is ongoing.
"The early signs of many cancers can be very non-specific and overlap with other diseases," Dr. Fryer says. "This is your dog’s way of telling you that they do not feel well. Listen to your dog."
Related: How To Decode Your Dog's Body Language
7. Persistent coughing or difficulty breathing
Yes, dogs can catch colds and get congested, but coughing and breathing problems aren't always benign.
"These symptoms can be associated with lung cancer or other respiratory issues," Dr. Savageau says.
8. Pain
Dr. Simon says a sudden onset of pain (which pet parents may notice if their dog is limping), could be a sign of bone cancer or osteosarcoma.
"The area affected may be swollen and very tender to touch," Dr. Simon says. "Owners who bring their pets in to see me with these lesions often assume the dog has pulled a muscle or is perhaps experiencing an arthritis flare-up."
Dr. Fryer says limping isn't the only sign your dog is in pain. Others include:
Does not want to be petted in a specific area
Chronic licking of one area
Hesitation to lie down on one side
Panting more
Going up and down stairs slowly
Doesn't want to be picked up anymore
Related: Keep Your Pup Playful and Happy—9 Ways To Fill Your Dog’s Emotional Cup, According to Pet Experts
What To Do if You're Concerned About Your Pet's Health
Your dog's vet is your best resource if you are worried about your pup.
"When your dog is not acting normally, it is best to reach out to your veterinarian," Dr. Fryer says.
You can help your vet gain more insights.
"If your dog has new or growing lumps or skin lesions, it is helpful to take serial pictures over the days or weeks that you waited for the vet appointment to show how the area has changed," Dr. Fryer says. "Placing a coin next to the area can help show the size. If you have videos of something that happens only sporadically at home, such as an intermittent limp or occasional cough, these are extremely helpful for your veterinarian."
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