Does My Pet Have Cancer? The Early Signs Pet Owners Need to Know

Approximately 1 in 4 dogs and 1 in 5 cats will develop cancer during their lifetime, with risk increasing as pets age. Cancer has become a leading cause of death in older pets. The good news? When caught early, many types can be managed effectively. Being aware of warning signs and acting quickly makes all the difference.

Spotting the Warning Signs

Your pet can't tell you when something's wrong, so stay observant. The most obvious sign is a lump or mass that continues to grow. Not all lumps are cancerous (some are harmless fatty deposits), but any growth that changes in size needs examination. This is especially important for cats, as they're experts at hiding illness and may not show obvious signs until cancer is advanced.

If your pet is losing weight despite eating normally, this could signal internal problems. Significant weight loss over a few weeks is particularly concerning. A pet who suddenly shows less interest in food, has difficulty chewing, or develops bad breath may be dealing with oral cancer. Cats may also start drooling excessively or paw at their mouth.

Watch for bleeding from the mouth, nose, or other body openings without obvious cause, including blood in stool or urine. Persistent vomiting or diarrhea that doesn't respond to treatment could indicate digestive system cancer. Chronic coughing, labored breathing, or retching may suggest lung problems or respiratory tract cancer. Cats with breathing difficulties may breathe with their mouths open or show rapid chest movements.

Limping that doesn't improve or has no clear cause needs investigation. Lumps under the jaw, in front of shoulders, or behind knees could be swollen lymph nodes indicating lymphoma (one of the most common cancers in both cats and dogs). Wounds that refuse to heal, even with treatment, may be more than simple injuries. In cats, watch for changes in litter box habits, as difficulty urinating or straining could indicate bladder or urinary tract cancer.

What to Do If You Notice These Signs

Don't panic, but don't wait. Early detection significantly improves treatment outcomes. Visit your veterinarian for a thorough physical examination. Share when you first noticed the problem, whether it has changed, and any other symptoms or behavioral changes. For cats especially, mention even small changes like spending more time alone or decreased interest in play, as these can be important clues.

Be prepared for diagnostic tests like blood tests, X-rays, ultrasounds, or tissue samples.

How Veterinarians Diagnose Cancer in Pets

Your vet starts with a comprehensive physical examination, checking for lumps and assessing vital organs. For cats, this exam is particularly thorough as they often don't show external signs until cancer is more advanced. X-rays visualize internal structures, detecting tumors in the chest or abdomen and checking if cancer has spread to lungs or bones. Ultrasound examines soft tissue masses and internal organs like the liver, spleen, and kidneys.

Among the tools your vet uses, ultrasound is often the best place to start when checking for possible tumours inside the body. Most pets don't need to be sedated or put under anaesthesia for an ultrasound. They simply lie on their side while the vet moves a small probe over the area. It's completely painless, and your vet can see what's happening inside your pet's body in real time on a screen.

This matters for two reasons. First, general anaesthesia always carries some risk, especially for older pets or pets who are already feeling unwell. Avoiding anaesthesia when possible is simply safer. Second, there's a big difference in cost. Imaging procedures that require general anaesthesia, such as CT scans or MRI, can cost 10 to 20 times more than an ultrasound. For many pets, an ultrasound gives the vet enough information to understand what's going on and plan the right next steps, without putting your pet through unnecessary risk or expense.

Blood tests reveal markers suggesting organ function and overall health status. These tests are especially helpful for cats, as changes in blood cell counts or organ function can provide important diagnostic clues. For accessible lumps, your vet may perform fine needle aspiration, which uses a needle to collect cells for microscopic examination with sedation. For definitive diagnosis, tissue biopsy involves taking a small sample sent to a specialized laboratory. The pathologist examines it microscopically, reporting whether it's benign or malignant, the tumor type, and aggressiveness level. Sometimes complete surgical removal serves both diagnostic and treatment purposes. Your vet will explain each recommended test and provide cost estimates upfront.

Treatment Options

Surgical removal remains the most common and often most effective treatment for many cancers. If caught early before spreading, surgery can sometimes provide a complete cure. Cats generally tolerate surgery well and can recover quickly when properly cared for.

Chemotherapy, performed at specialty centers, is recommended for certain cancers. Approximately 80% of animals don't develop significant side effects. For those who do, symptoms can usually be managed and are typically short-lived. Less than 5% require hospitalization for adverse effects. Cats tend to handle chemotherapy better than dogs, often with fewer side effects.

Radiation therapy treats specific cancers where surgery isn't feasible or as follow-up treatment. Immunotherapy, a newer approach helping the immune system fight cancer, is becoming more available for both cats and dogs.

When cure isn't possible, palliative care focuses on comfort and quality of life through pain management, nutritional support, and monitoring. Your vet will discuss prognosis, side effects, costs, and quality of life to help you make informed decisions. For complex cases, referral to a veterinary oncologist provides access to advanced therapies and specialized care.

Contagiousness to Other Pets?

The rare exception is transmissible venereal tumor in dogs, spreading through direct contact during mating. Some cancers are associated with viruses pets can acquire (like feline leukemia virus in cats, which can increase cancer risk), but the cancer itself doesn't spread from pet to pet.

However, this is a good reminder to keep all pets current on vaccinations, especially for cats who should be vaccinated against FeLV if they go outdoors or have contact with other cats. Maintain regular parasite prevention for all pets.

Why It Happens

Cancer results from genetic damage to cells. Normal cells follow instructions to grow, divide, work, and die in an orderly way. Cancer develops when damaged cells survive and replicate instead of dying, forming tumors or traveling through the bloodstream to other parts of the body.

Age increases risk, as more cell divisions over time mean more opportunities for genetic mistakes. This is why cancer is more common in senior pets. For dogs, this typically means over 7-8 years, while cats often develop cancer later, around 10-12 years or older.

Some pets have inherited tendencies toward specific cancers, though this is less common in mixed breeds and domestic cats compared to purebred animals. Secondhand smoke affects pets just as it does humans, increasing cancer risk in both cats and dogs. Cats who live with smokers face higher rates of lymphoma and mouth cancer, partly because they groom themselves and ingest smoke particles from their fur.

Obesity is linked to increased cancer risk in both species. In Singapore's heat, indoor pets can become less active, making weight management important. Maintain healthy weight through exercise during cooler hours for dogs and regular play sessions for indoor cats. Feed portion-controlled, balanced diets appropriate for your pet's age and activity level.

Hormones fuel certain cancers. Unspayed female cats and dogs have higher risk of mammary tumors, while unneutered males face reproductive cancer risks. Spaying and neutering significantly reduces these risks and is generally recommended unless you're breeding your pet.

Immune system function varies between individual animals. Some pets are born with weaker defenses, others develop them over time. When repair mechanisms can't keep up with cellular damage, mutations accumulate and can lead to cancer. Despite all we know about risk factors, pinpointing why one particular pet develops cancer is usually impossible.

Prevention and Early Checks

Annual health checks are recommended for adult pets, and every six months for seniors (typically over 7-8 years for dogs and over 10 years for cats). These routine visits catch changes early before they become serious problems.

Get to know your pet's normal body and behavior. For dogs, feel for lumps during grooming and watch for changes in energy, appetite, and bathroom habits. For cats, monitor eating patterns, litter box use, grooming behavior, and activity levels. Because cats hide illness instinctively, even small changes matter. Increased sleeping, decreased interaction, or changes in vocalization can all be important signals.

Maintain healthy weight through appropriate exercise and balanced, portion-controlled feeding. For dogs in Singapore's climate, walk during cooler hours like early morning or evening. For cats, provide regular interactive play sessions to keep them active, especially if they're indoor-only.

Minimize harmful exposure by keeping pets away from cigarette smoke (this is especially important for cats who groom themselves constantly). Limit sun exposure for light-colored animals or those with thin coats, particularly between 10am-4pm when UV levels are highest. Provide shade during Singapore's hot months and use pet-safe products in your home and garden.

For older pets, consider annual blood work to detect problems before symptoms appear. This is particularly valuable for cats, as they're so skilled at hiding illness. If you notice anything unusual (no matter how small), visit your vet. Early detection dramatically improves outcomes, and there's no such thing as being too cautious about your pet's wellbeing.

Moving Forward with Knowledge and Hope

Understanding cancer empowers you to be your pet's best advocate. By staying informed, being observant, and seeking veterinary care when needed, you're giving your companion the best chance at a long, healthy life. This is especially important for cat owners, as cats won't show you something's wrong until you notice the subtle signs yourself.

If you're concerned about changes in your pet's health, consult your veterinarian. Recognizing problems early (before your pet is obviously sick) makes the biggest difference in treatment success. Armed with this knowledge, you're better prepared to protect them.

At My Family Vet Clinic & Surgery in Bukit Batok, we're dedicated to providing compassionate, expert care for Singapore's pets. If you have concerns about your pet's health, we're here to help. Visit us at our walk-in clinic or reach us here.