Cancer in Dogs and Cats: Early Warning Signs to Know

Cancer is one of the most common causes of serious illness in older dogs and cats. Many cancers can be treated successfully, sometimes cured with surgery, when they are found early. The aim of this guide is not to frighten you. It is to help you notice the signs that are worth getting checked.

Warning signs worth acting on

A new lump, or a lump that is growing, changing shape, becoming red or ulcerating
A sore that doesn't heal in 2–3 weeks
Weight loss without diet change
Loss of appetite, or difficulty eating or swallowing
Bleeding or discharge from the mouth, nose, vagina, penis or rectum
A bad smell from the mouth or anywhere on the body
Lameness or a hard swelling on a bone in a large-breed dog
Persistent cough or breathing changes
Difficulty urinating or passing stool, or blood in either
Enlarged lymph nodes: firm swellings under the jaw, in front of the shoulders or behind the knees
Pale gums, weakness or a swollen belly, which can mean an internal tumour that is bleeding (an emergency)

The lump rule: "see something, sample something"

You cannot tell whether a lump is benign or cancerous by feeling it, and neither can a vet. A fine-needle aspirate (FNA) is a quick test. A thin needle collects cells from the lump in a few seconds, usually with no sedation, and we examine the slide under the microscope in our in-house lab. Many fatty lumps (lipomas) can be identified on the spot. If the cells are suspicious or unclear, the sample, or the lump after surgical removal, goes to an external pathology lab for histopathology.

Measure a lump when you first find it (a photo next to a coin helps) and bring the measurements with you.

Cancers we commonly see in Pune and PCMC

Mammary (breast) tumours in unspayed female dogs and cats. Common, and about half in dogs and most in cats are malignant. Spaying before the first or second heat greatly reduces the risk. Check along both rows of nipples monthly.
Skin tumours: mast cell tumours (which can look harmless), and squamous cell carcinoma on white-eared or light-nosed cats exposed to strong sun.
Transmissible venereal tumour (TVT): common in Indian street dogs and dogs who mate freely. It causes bleeding or cauliflower-like growths on the genitals. TVT usually responds very well to chemotherapy.
Lymphoma: firm, painless swelling of several lymph nodes.
Bone tumours in large, heavy breeds.
Oral tumours: a mass on the gums, a bad smell, drooling, bleeding.

What happens next if it is cancer

Depending on the type and stage, options can include surgery (often curative for skin and mammary tumours removed early with good margins), chemotherapy (often better tolerated by pets than people), and palliative care focused on comfort. Before surgery, we check blood values and usually take a chest X-ray to look for spread. For some cancers, CT scanning at a referral centre helps plan treatment, and we coordinate this.

Lowering the risk

Spay female dogs and cats if you aren't breeding them.
Protect white cats from strong midday sun on balconies.
Do a monthly "lump check" while grooming.
Annual health checks, or every six months for pets over 8.

Frequently Asked Questions

Is a needle test painful or risky?
It's similar to a vaccination. The risk is very low, and the information can save a pet's life.

Should I wait and watch a small lump?
Sample it first. Many lumps are harmless, but some cancers look small and innocent early on.

Is my pet too old for cancer treatment?
Age alone doesn't decide. Many older pets do well with surgery, and comfort-focused care is always an option.