Cancer in Cats: Symptoms by Body Area

Name: Cancer in Cats: Symptoms by Body Area
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

Cancer is common in older cats, and the signs often depend on where the tumor grows. Knowing the cancer in cats symptoms that show up in each body area helps you spot problems early and get your cat seen sooner. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Skin lumps and non-healing sores are the most common tumor signs owners can actually see, because skin tumors are the most frequently diagnosed tumors in cats [1].
Lymphoma is a cancer of the blood and lymphatic system, and it often starts in the intestinal tract or lymph nodes before spreading elsewhere [1][2].
Mouth, nasal, bladder, and eye tumors each have their own early clues, such as drooling, one-sided nosebleeds, straining to urinate, or a darkening iris [3].
Older age is the strongest predictor of cancer in cats, so senior cats need more frequent checkups, not fewer [4].
Any lump that grows quickly, any sore that will not heal in two weeks, and any sudden weight loss deserve a vet visit.

Cancer in Cats Symptoms by Body Area

Skin and Under the Skin

Skin tumors are the most commonly seen tumors in cats, partly because you can see them and partly because skin is constantly exposed to carcinogens in the environment [1]. Chemical carcinogens, solar radiation, and viruses can all cause skin tumors, and hormones and genetics may play a role too [1].

Watch for a new lump or bump anywhere on the body. Pay attention to lumps that change size, feel fixed to the tissue underneath, or bleed. Also watch for crusty, scabby, or scaly patches that do not heal. One reported cat had long-standing crusty skin lesions on the ear flaps, neck, and belly that turned out to be a form of squamous cell carcinoma in situ linked to papillomavirus infection [5]. That cat had no itching, which shows that skin cancer does not always look irritated.

Squamous cell carcinoma is one of the most common cancer types in cats overall, and fibrosarcomas and adenocarcinomas are also frequent [6]. Sun exposure matters most on light-colored skin, especially on the ear tips, nose, and eyelids.

Lymphoma and the Lymphatic System

Lymphoma, also called lymphosarcoma, is a cancer of the blood and lymphatic system [1]. It usually begins in other parts of the body, such as the intestinal tract or the lymphatic system, and can sometimes spread to the skin [1]. Lymphoma occurs in middle-aged to older cats, and no breed is known to have a higher risk than others [2].

Infection with feline leukemia virus and feline immunodeficiency virus both increase the risk of lymphoma [1][2]. Cats with lymphoma often show vague signs first, such as appetite loss, weight loss, vomiting, diarrhea, or low energy. You may feel enlarged lymph nodes under the jaw, in front of the shoulders, or behind the knees. Some cats have trouble breathing if the chest is involved.

A rare form of lymphoma can first appear as lymphoid infiltrations of the skin, causing distinctive tumors [1]. There are two forms of skin lymphoma, epitheliotropic and nonepitheliotropic [1]. If your cat has both skin lumps and general illness, your vet may consider lymphoma.

Mouth Cancer in Cats Symptoms

Mouth cancer in cats symptoms often show up as changes in eating and grooming. Watch for drooling, dropping food, chewing on one side, bad breath that is new or much worse, and reluctance to eat hard food. You may see a visible mass under the tongue, on the gums, or on the roof of the mouth. Sometimes the only sign is a swollen face or jaw.

Weight loss and bleeding from the mouth are also common. Squamous cell carcinoma is one of the most frequently diagnosed cancers in cats and often affects the mouth [6]. These tumors can be aggressive, so early evaluation matters. If your cat has stopped eating or is losing weight, also read about Pancreatitis In Cats Symptoms and Symptoms Of Kidney Disease In My Cat, since other diseases can cause similar signs.

Nasal Cancer in Cats Symptoms

Nasal cancer in cats symptoms usually start as breathing changes. You may notice noisy breathing, a blocked nose that does not clear, or one-sided nasal discharge. The discharge may be clear, bloody, or thick. Nosebleeds from one nostril are a common clue. Some cats develop a swollen area over the bridge of the nose or below the eye, and some have watery eyes on the same side.

Sneezing that lasts for weeks and does not respond to treatment is another reason to have your cat checked. Many nasal problems in cats are infections or polyps, not cancer, so testing is needed to tell them apart. A tumor in the nose can also cause bad breath or a decreased sense of smell, which may lead to appetite loss.

Eye Cancer in Cats Symptoms

The most common primary tumor inside a cat's eye is widespread melanoma of the iris [3]. In these cases, the iris becomes progressively darker (dark brown or black) and develops an expanding irregular surface [3]. Pupil abnormalities, glaucoma (high pressure inside the eye), and an enlarged eye happen late in the disease [3].

Feline lymphosarcoma-leukemia complex is a common tumor of the eye [3]. Cats with this condition may have signs in one or both eyes, such as inflammation and swelling of the cornea or uvea, excessive formation or rupture of blood vessels in the eye, retinal detachment, abnormal pupil size or shape, and lack of pupil dilation [3]. Slow healing sores may also occur, and some cats have signs of severe body-wide illness [3]. Tumors can be found in the orbit, eyeball, conjunctivae, and eyelids [3].

If your cat's eye looks cloudy, red, or different in color from before, get it checked. Removal of the eyeball is recommended when iris masses are fast-growing, because they may spread to other parts of the body [3].

Bladder and Urinary Tract

Bladder cancer in cats symptoms often look like a urinary problem. Watch for straining to urinate, urinating in small amounts, blood in the urine, or going outside the litter box. Some cats cry out while urinating. These signs overlap with much more common problems like urinary infections and bladder stones, so you cannot tell the difference at home.

If your cat is straining to urinate and nothing comes out, that is an emergency. A blocked cat can become critically ill within hours. For related reading, see Cat Urinary Infection Symptoms and Symptoms Of Urinary Tract Infection In A Cat.

Mammary Glands

Feline mammary carcinoma is an aggressive cancer in cats [7]. It often shows up as one or more firm lumps in the mammary chain along the belly, from the armpit to the groin. These lumps may be small at first. Because feline mammary tumors tend to be aggressive, early removal offers the best chance of control [7]. Check your cat's belly during regular petting, especially if she is middle-aged or older.

Intestinal Tract and Abdomen

Intestinal lymphoma often causes vomiting, diarrhea, weight loss, and a poor appetite. You may notice a bloated or tender belly. Some cats have intermittent signs that come and go for weeks, which can delay diagnosis. A vet may feel a thickened loop of intestine or an abdominal mass during an exam.

What Causes These Tumors

Cancer happens when cells grow out of control [2]. In cats, several factors raise the risk. Viruses matter a great deal. Feline leukemia virus and feline immunodeficiency virus both increase lymphoma risk [1][2]. Papillomavirus has been linked to some skin cancers in cats [5]. Sun exposure drives squamous cell carcinoma on light-colored ears and noses [1]. Age is the strongest single predictor, with older cats far more likely to develop cancer [4]. Genetics and hormones may also play a role in skin tumors [1].

Cause	Typical clues	How urgent
Skin tumor (various types)	New lump, crusty patch, non-healing sore, often on ears or nose	Routine visit, sooner if growing fast
Lymphoma	Weight loss, vomiting, diarrhea, enlarged lymph nodes, low energy	See vet within days
Oral tumor	Drooling, bad breath, trouble eating, visible mass	See vet within days
Nasal tumor	One-sided discharge or nosebleed, noisy breathing, facial swelling	See vet within days
Eye tumor	Darkening iris, cloudy eye, pupil changes, eye enlargement	See vet within days
Bladder tumor	Straining to urinate, blood in urine, small frequent urination	Same day if straining with no urine
Mammary tumor	Firm lump in the belly chain	See vet within days

Red Flags That Mean Emergency Now

Some signs cannot wait. Go to an emergency clinic right away if your cat is straining to urinate and producing little or no urine. This can be fatal within hours. Other emergencies include open-mouth breathing, especially at rest, sudden collapse, uncontrolled bleeding from the mouth or nose, a rapidly swelling face or neck that affects breathing, and a seizure that does not stop.

Call your vet the same day for a lump that appeared suddenly and is growing fast, a sore that has not healed in two weeks, vomiting that lasts more than a day, or a cat that has stopped eating for more than 24 hours. These signs are not always cancer, but they need prompt evaluation.

Safe Things You Can Do at Home While Waiting

You cannot treat cancer at home, but you can make your cat more comfortable and give your vet better information.

Take photos of any lump or sore with a ruler or coin next to it for scale. Note the date.
Measure your cat's food intake and weigh her weekly on a baby scale if you have one.
Keep a simple log of vomiting, diarrhea, appetite, and energy level.
Offer soft, warm, smelly food if eating is hard. Try small meals more often.
Keep fresh water available and consider adding a little warm water to canned food to boost fluid intake.
Do not give any human pain medication. Many are toxic to cats. Ask your vet before giving anything.
Keep your cat indoors and away from other cats if she seems unwell.

If your cat has a skin lesion, do not apply human creams or ointments unless your vet prescribes them. Some products are harmful if licked off.

What Your Veterinarian Will Check and Test

Your vet will start with a full physical exam, feeling every lymph node, checking the mouth and eyes, and palpating the belly. They will ask about appetite, weight, litter box habits, and how long signs have been present.

Common next steps include blood work, a urinalysis, and imaging such as X-rays or ultrasound. For lumps, the vet may do a fine needle aspirate, which pulls a few cells with a thin needle for review. A biopsy gives a larger tissue sample and is often needed for a firm diagnosis. For nasal signs, a scope exam or advanced imaging may be recommended. For eye changes, an eye exam with pressure measurement helps identify glaucoma [3].

If lymphoma is suspected, your vet may test for feline leukemia virus and feline immunodeficiency virus, since both raise the risk [1][2]. Treatment depends on the tumor type and location. Options can include surgery, chemotherapy, radiation, or topical therapy. One cat with multicentric squamous cell carcinoma in situ went into complete remission after topical imiquimod cream was applied twice weekly for three months, with two mild recurrences later controlled by a short repeat course [5]. That is one case report, so your vet will tailor any plan to your cat.

Doses for any medication are calculated by your veterinarian based on your cat's weight and health. Never guess a dose at home.

Prevention and Monitoring

You cannot prevent all cancers, but you can lower some risks and catch problems early.

Keep your cat indoors to reduce virus exposure and sun damage.
Test new cats for feline leukemia virus and feline immunodeficiency virus, and keep vaccinations current.
Limit sun exposure for light-colored cats, especially during peak hours.
Spay your cat. Mammary tumors are less common in cats spayed before their first heat.
Do a monthly home check. Run your hands over the whole body, look in the mouth, check the eyes, and feel the belly.
Schedule twice-yearly vet visits for cats over 10 years old, since age is the strongest predictor of cancer [4].
Track weight. A slow drop of even a few ounces matters in cats.

Limitations and When to Contact a Veterinarian

No article can tell you whether your cat has cancer. Only a veterinarian can examine your cat, run tests, and make a diagnosis. Individual cases need a veterinarian, and signs that look mild can still be serious.

Contact your vet the same day for a fast-growing lump, a sore that will not heal, new drooling or trouble eating, one-sided nosebleeds, a changing iris, or straining to urinate. Go to an emergency clinic now for open-mouth breathing, collapse, uncontrolled bleeding, or a cat that cannot urinate at all. For routine concerns like a small stable lump or a mild change in appetite, book a visit within a week.

Frequently Asked Questions

How common is cancer in cats?

Cancer is a leading cause of illness and death in middle-aged and older cats [4]. In one large hospital record review, about 17 percent of cats seen were diagnosed with cancer [4]. Age was the strongest predictor in that group [4].

Can a cat survive lymphoma?

Yes, many cats with lymphoma live for months to years with treatment, though survival varies by tumor location and virus status. Cats with lymphoma and feline leukemia virus infection have lower overall survival times [3]. Your vet can give you a realistic outlook after staging.

Do all lumps on cats turn out to be cancer?

No. Many lumps are benign, such as cysts, lipomas, or reactions to injury. Skin tumors are the most common tumors in cats, but that includes both benign and malignant types [1]. A fine needle aspirate or biopsy is the only way to know for sure.

Is mouth cancer in cats painful?

Often yes. Cats with oral tumors may drool, drop food, or refuse to eat because chewing hurts. Some cats hide pain well and only show weight loss or bad breath. Pain control and nutritional support are part of care.

Can I catch cancer from my cat?

No. Cancer itself is not contagious between cats and people. Some viruses that raise cancer risk in cats, such as feline leukemia virus, do not infect humans. Still, wash your hands after handling sores or body fluids as good hygiene.

References

Tumors of the Skin in Cats - Cat Owners. Merck Veterinary Manual.
Immune System Tumors in Cats - Cat Owners. Merck Veterinary Manual.
Cancers and Tumors of the Eye in Cats - Cat Owners. Merck Veterinary Manual.
Descriptive epidemiology of canine and feline cancer in California, United States from 2000 to 2019. Veterinary journal (London, England : 1997), 2026.
Coinfection with Different Feline Papillomaviruses in a Cat with Multicentric Squamous Cell Carcinoma In Situ. Animals : an open access journal from MDPI, 2026.
Factors influencing malignant tumor development in cats from a multicenter retrospective study. Scientific reports, 2026.
Feline Mammary Carcinoma as a Comparative Model of Human Breast Cancer: An Integrative Review. Cancers, 2026.