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Nobody wants to think about the “C-word,” but unfortunately, cancer is a leading cause of death among dogs. According to veterinary oncologist Dave Ruslander, 50% of dogs over age 10 will develop a type of cancer.
As the body ages, its disease-fighting immune system weakens, and it becomes more vulnerable to disease. It’s important, therefore, to learn the early signs of cancer and the different types of canine cancer to keep your dog as healthy as possible for as long as possible—in addition to providing a wholesome diet, age-appropriate exercise, and mental stimulation.
If you do suspect a problem, consult with your vet to learn about treatment options. We also highly recommend the Dog Cancer Survival Guide, written by expert veterinarians, to help you make the best decisions for your dog’s care.
Keep in mind—early detection is key to optimizing your dog’s options for successful cancer treatment and improving his overall quality of life.
Tumors, mysterious swellings, and unusual growths
Although it’s probably the first symptom that comes to mind when you think about cancer in dogs, tumors are not always cancerous. As dogs age, they’re more likely to develop fatty deposits and other benign lumps.
But some growths can be malignant, and tumors can signal skin cancer, mammary cancer, and other types of cancer. Skin tumors are one of the most common types of growths your dog could develop, so be on the lookout for these.
Swollen lymph nodes are another thing to watch for. These lumps don’t cause pain, but they can indicate lymphoma—one of the most common types of cancer in dogs, particularly in Golden Retrievers. Swollen lymph nodes could also signal leukemia or a different type of cancer that has metastasized (or spread), causing inflammation of the lymph nodes.
You can perform a monthly “lump check” to keep track of your dog’s lumps and bumps. This is especially important for older dogs who develop benign growths all the time.
With practice, you can learn how to tell the difference between a benign fatty deposit and a more concerning growth. But if a new lump or swelling develops, it’s a good idea to check with your expert veterinarian just in case.
Wounds that won’t heal
Like tumors, persistent wounds can be signs of cancer in dogs. Typically, a small wound or lesion should heal over time, with visible signs of healing (i.e. scabbing and skin and hair regrowth). If your pet has a recurring lesion or wound that just won’t heal, it’s time to see the vet to rule out cancer or another serious health issue.
Red, irritated lesions could indicate mast cell tumors, one of the most common skin tumors found in dogs. Though more commonly found on the skin, MCTs can also spread to bone marrow or other organs.
“Lameness” is a change in your dog’s regular gait. It may present as tenderness and subtle pain, limping or favoring a limb, or in severe cases, the inability to place any weight on the limb. Basically, lameness = pain, and it can be an indication of bone cancer, particularly in older dogs.
You don’t need to panic about every little hitch in your dog’s step (particularly if they’re an older dog with arthritis), but sudden, persistent lameness should be evaluated by a vet.
Sudden, persistent lameness should be evaluated by a vet
Rapid, unexplained weight loss or gain
Weight loss is a particularly common sign of cancer in dogs and may indicate a gastrointestinal tumor that’s otherwise undetectable from the outside. If your dog starts losing weight rapidly, whether their appetite changes or stays the same, get to the vet ASAP.
Sudden weight gain or bloating can also be a sign of canine cancer. If your dog maintains their regular appetite but seems to gain weight quickly, it’s time for a check-up.
Abnormal discharge or bleeding
Abnormal discharge or bleeding anywhere on the body is cause for concern, but this dog cancer symptom is most visible on the face. Funky eye discharge or a sudden bloody nose can indicate certain types of canine cancer, such as eye and skin cancers.
Similarly, sores and bleeding in the mouth can be a sign of oral tumors, which often go undetected because people assume the discharge and odor is a normal sign of aging. While bad breath is common in older dogs, unusual odor, discharge, or bleeding is cause for concern.
Old dogs slow down. It’s an unfortunate but unavoidable fact of doggy life. However, a sudden, unexplained lack of energy—lethargy—can be a sign of illness or disease.
Lethargy is different from plain old tiredness in that it alters your dog’s enthusiasm level. They may suddenly lose interest in a favorite toy or activity, or fail to get up and greet you when you come home from work. Other signs of lethargy may include excessive sleep and delayed responses to visual and auditory stimuli.
Lethargy is a general symptom of a broad range of issues, so it doesn’t automatically signal cancer. But if your dog is suddenly a lot less active than usual, something could be going on.
You know your dog, and you see her “output” every day. You probably have a sense of the difference between normal poop, somebody-got-into-the-cat-food-again poop, and something more concerning. Persistent diarrhea, hardened stools, and straining can all be symptoms of cancer in dogs.
If you’re concerned about something in your dog’s output, don’t hesitate to call the vet. In particular, watch for black, tarry stools, which can indicate ulcers, a symptom of mast cell tumors (source).
If you’re concerned about something in your dog’s output, don’t hesitate to call the vet.
Difficulty breathing or going to the bathroom
One of the most common (and alarming) signs of illness or injury is when normal bodily functions become labored or painful. If your dog is having trouble breathing, straining to go to the bathroom, or otherwise seems uncomfortable during normal activities, don’t hesitate to have her checked out. Sudden, extreme discomfort or pain are important warning signs that shouldn’t be ignored.
The Bottom Line
Cancer is scary, but you don’t have to live in fear of it. Remember: modern dogs live a lot longer than their ancestors did. The fact that dogs routinely live beyond age ten is a great indication of how far pet care and veterinary medicine have advanced.
The good news—canine cancer treatments have improved significantly, and pet owners now have the option to pursue treatments like surgery, chemotherapy, and radiation therapy.
So track your dog’s health, and see the vet if you notice something unusual. The rest of the time, continue enjoying life to the fullest with your four-legged best friend.