Recognizing the Warning Signs: A Pet Owner’s Guide to Common Cancers

Cancer is one of the most significant health challenges our pets may face—especially as they age. According to the American Veterinary Medical Association (AVMA), nearly 50% of dogs over the age of ten will develop some form of cancer. For cats, the numbers are also significant, particularly in their senior years.

Just like in people, cancer in pets can vary widely in how it looks, how fast it grows, and how it affects the body. But here’s the good news: early detection can make all the difference. Catching cancer early is like spotting smoke before it becomes a wildfire—it gives you a better chance to act quickly and effectively.

What Exactly Is Cancer?

Cancer is a disease of uncontrolled cell growth. In a healthy pet, cells grow, divide, and die off in a balanced cycle. But with cancer, that balance is lost. Abnormal cells begin multiplying too fast or living too long, often forming tumors.

These tumors fall into two broad categories:

  • Benign Tumors: Think of these like a bump in the road that’s annoying but not dangerous. They don’t spread or invade other tissues.
  • Malignant Tumors: These are the serious ones—cancerous and capable of invading nearby tissue or spreading to other parts of the body (a process called metastasis).

Common Types of Cancer in Pets (and What to Watch For)

Each type of cancer has its own “personality”—its own warning signs, locations, and treatment options. Here’s a breakdown of the most commonly seen cancers in dogs and cats.

Lymphoma

What it is: Cancer of the lymphatic system (part of the immune system).
Common signs: Swollen lymph nodes (especially under the jaw or behind the knees), lethargy, weight loss.
How it’s treated: Typically with chemotherapy.
 More info from the Veterinary Cancer Society

Analogy: Think of the lymphatic system like your pet’s internal highway for immune traffic—when lymphoma occurs, that highway is clogged with harmful, overactive cells.

Hemangiosarcoma

What it is: An aggressive cancer of the blood vessels, often affecting the spleen, heart, or skin.
Common signs: Sudden weakness, collapse, pale gums, internal bleeding.
How it’s treated: Emergency surgery, chemotherapy, or both.
 Read more at Cornell Vet

Analogy: Imagine a water balloon with a weak spot—it can rupture at any time. That’s what hemangiosarcoma can be like, particularly in the spleen.

Mast Cell Tumors

What it is: A common skin cancer in dogs that may look harmless at first.
Common signs: Swollen, itchy, or ulcerated lumps—may change size rapidly.
How it’s treated: Surgery, radiation, chemotherapy.

Analogy: These tumors are like biological tricksters—they may seem innocent, but beneath the surface, they can be serious. Always investigate suspicious lumps.

Squamous Cell Carcinoma (SCC)

What it is: A type of skin cancer often affecting cats—particularly the nose, ears, and mouth.
Common signs: Non-healing sores, facial swelling, drooling, or difficulty eating.
How it’s treated: Surgery, radiation, sometimes chemotherapy.
 Read more from the Cornell Feline Health Center

Analogy: SCC is like a persistent wound that refuses to heal—because it’s not really a wound at all. It’s a cancer in disguise.

Osteosarcoma

What it is: A fast-growing bone cancer, most common in large-breed dogs.
Common signs: Limping, swelling of limbs, pain, reluctance to move.
How it’s treated: Amputation, chemotherapy.

Analogy: This is like a crack in the foundation of a house. It starts with a limp but can quickly weaken the entire limb and spread without treatment.

Signs of Cancer in Pets: What Should You Watch For?

Like a detective searching for clues, pet owners should be alert to any unusual changes. Cancer often whispers before it shouts. Here are some signs that deserve your attention:

  • New or changing lumps or bumps
  • Unexplained weight loss or reduced appetite
  • Lameness that doesn’t improve
  • Difficulty eating, swallowing, or breathing
  • Persistent sores, bleeding, or discharge
  • Behavior changes such as hiding, restlessness, or decreased activity

More warning signs from AAHA

How Is Cancer Diagnosed in Pets?

Diagnosing cancer is like assembling a puzzle—no single test gives the full picture. Your veterinarian will combine several tools to arrive at a diagnosis:

1. Physical Exam and Medical History

  • Your vet will check for any abnormal masses or symptoms and ask about changes you’ve observed at home.

2. Cytology and Biopsy

3. Imaging

  • X-rays show bone involvement and look for metastasis.
  • Ultrasound evaluates internal organs.
  • CT and MRI give high-detail images for complex or deep tumors.

4. Bloodwork and Lab Tests

  • Assess organ function, detect abnormalities, and evaluate cancer’s impact on overall health.

Cancer Treatment Options for Pets

Treatment depends on the type, stage, location, and overall health of your pet. Here are the most common approaches:

Surgery

  • Removes localized tumors completely or partially to relieve symptoms.

Chemotherapy

  • Targets cancer cells throughout the body. Contrary to what many believe, pets often handle chemo better than humans—most experience minimal side effects.

Radiation Therapy

  • Especially helpful for tumors in sensitive or inoperable areas.

Immunotherapy and Targeted Therapies

  • These newer treatments act like guided missiles—targeting only cancer cells while sparing healthy ones.

Living with a Cancer Diagnosis: What Pet Owners Should Know

A cancer diagnosis isn’t always a goodbye—it can be a call to action. Many pets respond well to treatment and continue to enjoy a good quality of life. Managing cancer means managing the whole pet, not just the disease.

Comprehensive Care Includes:

  • Pain management and mobility support
  • Nutritional adjustments to maintain strength
  • Palliative or hospice care when curative treatment isn’t possible

Can You Prevent Cancer in Pets?

While not all cancers are preventable, some proactive steps can reduce risk and improve early detection:

Routine Veterinary Exams

Monitor Lumps and Changes

  • If you notice a lump, don’t wait. Schedule an exam—early evaluation can make all the difference.

Limit Carcinogen Exposure

  • Avoid secondhand smoke, minimize sun exposure for light-skinned pets, and steer clear of toxic household products.

Compassionate Cancer Care Starts with You

Cancer in pets is serious, but with early intervention, proper treatment, and ongoing care, many pets can continue living full, happy lives. Think of wellness exams and home monitoring as your pet’s best defense—like a smoke alarm for their health.

If your dog or cat has developed a lump, is losing weight, or just doesn’t seem like themselves, trust your instincts. Contact the team at Pinedale Animal Hospital to schedule an evaluation. We’re here to provide expert diagnostics, clear communication, and gentle, effective care—every step of the way.

Because every moment matters- let’s make sure they’re healthy ones.