Cancer (General)

Cancer is the leading cause of death in dogs over ten years old in the UK, accounting for approximately half of all deaths in this age group. But cancer is not a single disease - it encompasses many conditions, from highly treatable superficial skin tumours to aggressive internal cancers with poor prognoses. Early detection matters enormously because stage at diagnosis is the strongest predictor of outcome for most cancer types.

The challenge is that early-stage cancer often produces no specific signs. The monitoring habits that make a difference are the ones practised when nothing seems wrong.

Monthly home examination

A monthly full-body check - ideally at the same time each month - is the most effective at-home cancer monitoring tool for dogs over five years of age.

What to check:

• Lumps and bumps. Run your hands slowly over the entire body, feeling beneath the coat. Note any new lumps and any changes in existing ones. For each lump record: location, size (estimate or measure with a ruler), texture (soft, firm, moveable or fixed), whether it seems to bother the dog, and whether it's changed since last month.
• Lymph nodes. The most accessible lymph nodes in dogs are under the jaw (submandibular), in front of the shoulder (prescapular), in the armpits, and in the groin. Enlarged lymph nodes - palpably larger than a grape, firm, or multiple affected - warrant prompt veterinary assessment.
• Abdomen. A rounded or distended abdomen, or an area of firmness that wasn't there before.
• Oral cavity. With the mouth open, look at the gums, tongue, and back of the throat. New masses, ulcerated areas, or asymmetry.
• Eyes and face. Any bulging eye, facial swelling, or asymmetry.

Systemic signs to log

Beyond lumps, log monthly:

• Weight. Unexplained weight loss (without dietary changes) is a non-specific but sensitive early cancer sign.
• Appetite changes. Reduced interest in food is common in many internal cancers.
• Energy and exercise tolerance. Gradual decrease warrants investigation, particularly in older dogs.
• Cough or breathing changes. Persistent cough in an older dog, particularly one that doesn't have a history of respiratory disease, warrants chest X-rays.
• Pale gums. Pallor indicates anaemia - several cancer types cause significant anaemia (haemangiosarcoma rupturing causes acute collapse from internal bleeding; immune-mediated haemolytic anaemia can accompany lymphoma).
• Bleeding or discharge. Unexplained nosebleeds, bloody urine, or any unusual discharge.

Common cancer types in dogs

Mast cell tumours: Most common skin tumour in dogs; highly variable behaviour (grade 1 is often cured with surgery; grade 3 is aggressive). Any skin lump can be a mast cell tumour - fine needle aspirate is simple and inexpensive.

Lymphoma: Affects the lymphatic system; often presents with enlarged lymph nodes throughout the body. Responds to chemotherapy; median survival with treatment is 12–18 months.

Haemangiosarcoma: Aggressive cancer of blood vessel lining; most common in spleen (internal bleeding), skin (more treatable), and heart. Splenic haemangiosarcoma often presents with acute collapse from rupture.

Osteosarcoma: Bone cancer, most common in the long bones of large breeds. Extremely painful; presents as progressive lameness. Sadly carries a poor prognosis.

Mammary tumours: Common in unspayed females; 50% are malignant. Neutering before the first season nearly eliminates risk.

After diagnosis

If your dog is diagnosed with cancer, the monitoring focus shifts to:

• Treatment side effects (if chemotherapy or radiation is used)
• Quality of life indicators - appetite, energy, pain, engagement
• Tumour response (scheduled imaging or examination)
• Early recognition of complications

Ask your vet or oncologist specifically what to watch for during treatment and what signs warrant an early call.

When to contact your vet

Contact your vet soon if:

• You find a new lump that is firm, fixed to underlying tissue, or rapidly growing
• Lymph nodes are enlarged
• Unexplained weight loss over several weeks
• Persistent cough, difficulty breathing, or pale gums

Go to the emergency vet immediately if:

• Sudden collapse, pale gums, and rapid deterioration (could be internal bleeding from a ruptured tumour)

Frequently Asked Questions

All lumps I find - should I have them all checked? Any new lump warrants at least a fine needle aspirate - a quick, low-cost procedure where a needle is passed into the lump and cells are examined under a microscope. This can distinguish a lipoma (benign fatty lump) from a mast cell tumour or other concerning cell type. "Wait and see" on lumps leads to delayed diagnosis of treatable conditions.

My dog has been diagnosed with cancer - should I pursue treatment? This is a deeply individual decision and depends on the cancer type, the dog's overall health, the realistic outcomes of treatment, and the dog's quality of life during treatment. An oncology referral can give you the most informed picture of what treatment involves and what outcomes are realistic for your specific situation.

Does neutering prevent cancer? Early neutering eliminates the risk of pyometra and mammary tumours in females, and testicular tumours in males. The relationship between neutering and other cancers (lymphoma, osteosarcoma, hemangiosarcoma) is complex and breed-dependent. Discuss the timing of neutering with your vet in the context of your dog's specific breed risks.

Are there cancer screening tests for dogs? Blood-based cancer screening tests (liquid biopsy) for dogs are becoming available and are actively researched. They are not yet widely used in routine UK veterinary practice, but this is an evolving area. Regular physical examination and monitoring remain the most accessible tools currently.

My dog is twelve - if we find cancer, is it worth treating? Age alone is not a reason to forgo treatment. What matters is the dog's overall health, the type of cancer, the treatment required, and the realistic quality of life during and after treatment. A twelve-year-old dog in otherwise good health with a surgically removable Grade 1 mast cell tumour has an excellent outcome from surgery. A twelve-year-old dog with advanced internal cancer facing intensive chemotherapy is a different conversation. Assess each situation specifically.