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Cancer in Pets
Cancer is one of the leading causes of death in older pets. A diagnosis is frightening — but understanding the condition helps you make the most compassionate decisions for your animal.
Understanding Cancer in Pets
Cancer is not one disease — it is an umbrella term for over 100 different conditions, all characterised by abnormal and uncontrolled cell growth. Some cancers are slow-growing, localised, and may never significantly affect your pet's life. Others are aggressive, spread rapidly, and can cause significant suffering in a short period.
Cancer affects approximately 1 in 4 dogs and is the leading cause of death in dogs over the age of 10. It is less common in cats but incidence increases with age. Certain breeds are at higher risk — Golden Retrievers, Rottweilers, and Bernese Mountain Dogs have particularly high rates of specific cancers.
Common Types of Cancer in Pets
Lymphoma
One of the most common cancers in dogs and cats. Affects the lymphatic system — enlarged lymph nodes are often the first sign. Highly responsive to chemotherapy, with many dogs achieving remission.
Mast Cell Tumours (dogs)
The most common skin tumour in dogs. Behaviour is unpredictable — some are benign and cured by surgery; others are aggressive and require additional treatment. Grading by a pathologist is essential.
Osteosarcoma
Aggressive bone cancer, most common in large and giant breeds. Usually affects the limbs. Associated with severe pain and unfortunately carries a poor prognosis.
Haemangiosarcoma
A tumour of blood vessel cells, most commonly affecting the spleen and heart. Often silent until rupture causes acute internal bleeding. Common in German Shepherds and Golden Retrievers.
Mammary Tumours
The most common tumour type in entire female dogs. 50% are malignant. Entire female cats are also at risk. Risk is significantly reduced by early neutering.
Squamous Cell Carcinoma (cats)
Commonly affects the skin of white or pale cats, particularly the ears and nose. Solar radiation is the main risk factor. Also affects the oral cavity in cats.
Fibrosarcoma
A tumour of connective tissue. Can occur at injection sites in cats (Vaccine-Associated Sarcoma — VAS), though this is uncommon.
Brain Tumours
Can cause seizures, behaviour changes, or neurological signs. More common in brachycephalic breeds (Boxers, Boston Terriers). May be primary or secondary (from spread elsewhere).
Signs & Symptoms
The signs of cancer are varied and non-specific — many overlap with other conditions. If you notice any of the following, particularly in an older pet, a veterinary assessment is warranted:
Unexplained weight loss
Significant weight loss not explained by diet changes or increased exercise.
Abnormal swellings
Lumps that appear suddenly, grow rapidly, or change in character.
Sores that won't heal
Non-healing wounds or ulcerations on the skin or in the mouth.
Loss of appetite
Significant reduction in food interest, particularly combined with weight loss.
Bleeding or discharge
Unexplained bleeding from any body opening, or unusual discharge.
Difficulty breathing
Laboured, rapid, or noisy breathing. Coughing that doesn't resolve.
Difficulty eating or swallowing
Dropping food, reluctance to eat hard food, drooling.
Persistent lameness
Lameness that doesn't improve with rest or standard treatment.
Lethargy
Marked reduction in energy, interest, or engagement with life.
Changes in urination or defecation
Straining, frequency changes, blood in urine or faeces.
Diagnosis & Staging
Diagnosis of cancer requires more than a clinical examination. A biopsy — taking a sample of tissue for histopathological analysis — is the gold standard and provides information not just about whether cancer is present, but about its type and grade (how aggressive it is likely to behave).
Fine needle aspiration (FNA) is a less invasive option for sampling lumps and lymph nodes, providing cytological information. It is faster and cheaper than biopsy but gives less detail.
Staging — determining how far the cancer has spread — typically involves chest X-rays (to look for lung metastases), abdominal ultrasound, and sometimes CT or MRI scanning. Staging helps determine prognosis and guides treatment decisions.
Bloodwork (full haematology and biochemistry) assesses the impact of cancer on the body and identifies any organ compromise that might affect treatment options.
Treatment Options
Surgery
The primary treatment for many solid tumours. The goal is complete removal with clean margins. Surgery may be curative for localised, benign or low-grade tumours. For higher-grade cancers, surgery is often combined with other treatments.
Chemotherapy
Used for systemic cancers (lymphoma, leukaemia) or as an adjunct to surgery for high-risk tumours. Veterinary chemotherapy is generally better tolerated than human chemotherapy — the goal is quality of life, not cure, so doses are typically lower.
Radiotherapy
Used for tumours that cannot be fully removed surgically, or to treat areas where microscopic spread is likely. Requires specialist referral and multiple anaesthetics.
Targeted therapies
Newer agents such as toceranib (Palladia) target specific molecular pathways in certain tumour types. Represent a significant advance in veterinary oncology.
Palliative care
When curative treatment is not possible or not desired, palliative care focuses on controlling pain, maintaining appetite, and preserving quality of life for as long as possible. NSAIDs, steroids, and supportive medications all play a role.
Quality of Life & When Comfort Becomes the Priority
The decision about how aggressively to treat cancer is deeply personal, and there is no right or wrong answer. Factors to consider include: the type and stage of cancer, your pet's overall health and age, the likely response to treatment, the side effects and demands of treatment, and what your pet's life will look like during treatment.
For many owners, the goal shifts from "treating the cancer" to "giving the best possible remaining time." Palliative care, pain management, and focusing on the things your pet loves can provide excellent quality of life for weeks or months.
When cancer is causing uncontrollable pain, respiratory distress, inability to eat or drink, loss of interest in life, or when your pet is clearly suffering — these are the moments to consider whether a peaceful, planned farewell is the kindest option. A gentle death at home, in your arms, is something we can provide.
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