A recent study by the Morris Animal Foundation found that 41% of pet owners worry most about cancer when it comes to their pet’s health. This fear is not unfounded, as cancer is the leading cause of death in approximately 47% of dogs and 32% of cats. Unfortunately, cancer can be tricky to detect early, and routine bloodwork often isn’t enough.

The good news? Being aware of early warning signs can make a difference. According to the American Veterinary Medical Association (AVMA), there are 10 signs that should prompt a veterinary visit. These signs don’t necessarily mean your pet has cancer, but they could indicate a medical issue that needs attention—and early detection always helps lead to better outcomes.

Signs to Watch For

1. Abdominal Swelling

A swollen belly can develop gradually or suddenly. This could be due to a variety of causes. Your veterinarian will likely recommend bloodwork, a urine test, and an abdominal ultrasound to start to try to identify the cause.

2. Persistent Vomiting, Decreased Appetite, or Diarrhea

More than 3–4 vomiting episodes in a day or diarrhea lasting over 36 hours should prompt veterinary care. Dehydration can develop quickly and lead to additional consequences such as pancreatitis or kidney injury. Testing may include bloodwork, urine analysis, X-rays, and possibly an abdominal ultrasound. While many causes resolve with supportive care, cancer should also be ruled out.

3. Sudden or Unexplained Weight Loss

Weight loss is often one of the earliest signs of cancer in dogs and cats, with or without change to their appetite. If your pet is losing weight without a known cause, schedule an exam as soon as possible.

3. Difficulty Breathing

Any sign of labored breathing is an emergency. This may mean increased respiratory rate or effort, or in cats, open-mouth breathing can often be a sign of distress. If you see these signs, please seek immediate care from your primary veterinarian or your closest emergency clinic. X-rays and bloodwork are typically the first steps.

4. Bleeding From the Mouth, Nose, or Other Areas

Oral and nasal tumors are common in dogs and cats. Blood-tinged saliva, slowed eating, nasal bleeding or persistent nasal discharge should always be evaluated by a veterinarian.

5. Trouble Eating or Swallowing

This can indicate dental disease or something more serious. A prompt exam can help determine the cause and if additional diagnostics or treatment is warranted.

6. Lumps, Bumps, or Skin Changes

Every new mass should be checked, especially if it is changing in size, shape, or character. A simple needle aspirate—quick, minimally invasive, and usually painless—can reveal what the mass may be. Depending on the results, your veterinarian may recommend an incisional biopsy for more information, removal via an excisional biopsy, or monitoring. Many masses (like benign lipomas) are harmless, but only further testing can tell.

7. Non-Healing Wounds

If a sore isn’t improving after a few days to a week, it’s time for a veterinary visit. Cancerous tissue doesn’t heal normally and often continues to grow. Early evaluation opens the door to more treatment options and better outcomes.

8 Swelling, Heat, Pain, or Lameness

Persistent limping or swelling should be investigated promptly. Depending on your pet’s examination, x-rays may be recommended to further evaluate the bone and joints within the affected leg. Depending on the findings, additional testing such as a joint tap, CT scan, or biopsy may be recommended.

If Your Pet Is Diagnosed With Cancer

If your pet is diagnosed with cancer, your veterinarian may recommend a consultation with a veterinary oncologist. These specialists have more than eight years of advanced training dedicated specifically to diagnosing and treating cancer in dogs and cats. Depending on your pet’s needs, treatment may involve medical chemotherapy (given orally or by injection), surgery, radiation therapy, or a combination of these options.

Most pets handle cancer treatments much better than many people expect. No matter which approach is recommended, maintaining your pet’s comfort and quality of life is always our top priority. Some cancers can be cured, while others are managed long-term. When a cure isn’t possible, our focus shifts to providing your pet with the best quality of life for as long as possible.

You know your pet better than anyone. With clear information and a trusted veterinary team, you can feel confident making decisions that support your pet’s health and well-being.