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Lumps, Bumps and Skin Tumours in Cats


How often have you been patting your pet and discovered a lump? While cats have a much lower incidence of skin cancer than dogs, a higher percentage – over 50% – are malignant. That means, just like us, it’s very important to investigate promptly every unusual lump or skin mark you discover on your pet.

Typically, benign tumours grow slowly (if at all) and they are well circumscribed, non-painful and can remain unchanged for years. Malignant tumors are more likely to grow rapidly, have poorly defined margins, infiltrate into the surrounding tissues, and may be ulcerated.

While the list below does not cover all the skin tumours diagnosed in cats, these are some of the most common lumps and bumps.


Squamous cell carcinomas

Squamous cell carcinomas (SCC) are one of the most common and dangerous skin cancers in cats – especially cats with white ears and non-pigmented noses. The most common initiating cause of SCCs in both cats and dogs is sun exposure. The usual sites for this cancer are the tip of the nose, eyelids, lips and ear tips. It’s essential – as with white-skinned dogs – that cats with white noses, faces and ears are kept inside or, at the very least, allowed only minimal time in the sun.

SCCs in cats become invasive quickly and it's really important this skin cancer is diagnosed and treated promptly.

Clinical Signs

​Any crusty or bleeding sore that doesn't heal, especially if it's located in areas where the cat's fur is white or light coloured, is potentially a squamous cell carcinomas. This is the time to take your cat to the vet (even better, as soon as you notice a lesion in these white-haired vulnerable places). Tips of white ears can develop red, crusted and bleeding sores along the edges. If the sores are left to get larger, the ear tips will gradually disappear as the cancer erodes the tissues and the ear(s) will become increasingly malformed.


Early treatment includes surgery and/or cryosurgery (freezing), while more advanced cases require radiation or chemotherapy and have a poor prognosis. If the ear tips are affected, surgery to remove all the ulcerated tissue is usually effective - your cat may have a different appearance, but it will recover well.


Limit the amount of time your cat spends in the sun. If your cat spends a lot of time on the window sill during the day, a window shade or reflector to block UV rays is a sensible option. It's not out of the question to apply sunscreen to your cat's ears and nose before it goes out in the sun, or tattoos can be applied as a permanent sunscreen.



Soft fatty tumours are most often seen (or felt) in older cats. Overweight cats of any breed are more prone to lipomas, and while they can develop anywhere over the body, they occur mostly around the ribs and often as multiple lumps. While fatty tumours are benign (so won’t spread to other organs), it’s still important to find out if your cat's lump is in fact a benign fatty tumour. Diagnosis is easy – at CVH we take a fine needle aspirate from the lump and look at the tumour cells under the microscope. Fat cells are straightforward to diagnose.

Lipomas can grow to quite a large size and in some cases, will start to impact on a pet’s mobility. In these cases we recommend surgery to remove the tumour, otherwise all that’s usually required by the pet owner is regular monitoring of the tumour’s size and appearance once diagnosis is confirmed.


Mast cell tumours

Mast cell tumours in cats are usually seen on the head or neck. In healthy cats and dogs, mast cells occur throughout the body and help animals respond to inflammation and allergies. When they become cancerous, they can develop rapidly into serious, life-threatening disease.

Mast cell tumours are a good example of why it’s so important to have any lump or skin lesion examined promptly. They are very variable and can appear small and insignificant, but when first noticed they are usually raised and around 1 cm in diameter. They may be itchy or red and may periodically swell up and then disappear only to return again a few days later. This often confuses pet owners, who think because the mass disappears it can’t possibly be cancer.

While a lower percentage of mast cells are malignant in cats compared to dogs, early surgery to remove the lesion and prevent spread of the cells to other parts of the body is essential. Follow-up pathology to confirm the diagnosis is important to guide future treatment. If caught early enough, surgery will stop further spread.



In cats and dogs, melanomas are not related to sun exposure and they are not always malignant, and they are far less common in cats. The most dangerous occur in dark pigmented areas of the skin including inside the mouth, on the paws, or in the eyelid tissues. These pigmented areas may be normal for that pet – for example, a black Labrador – but any darkly pigmented, raised, thickened or ulcerated growth on your cat or dog needs to be checked promptly. Diagnosis by fine needle aspirate helps determine the course of treatment – that could mean surgery if the lump is easily removed.


Sebaceous cysts

These cysts are the result of blocked oil glands. They rarely grow to more than 1cm across and can occur anywhere over the body. They do appear to be more common in older pets and while it’s sensible to get veterinary advice to confirm the diagnosis, no treatment is required for sebaceous cysts.


Diagnosis and Treatment

Regardless of the size, shape or appearance of a new skin lesion or lump on your cat, please make sure you have a prompt check up. It’s often an easy exercise to determine if the lump needs immediate treatment or if it just needs monitoring over time.

The specific treatment for any lump and bump found in or on your cat’s skin will depend on the tumor's type, location, size, and whether the cancer has spread to other organs. If required, surgical removal of the tumor remains the treatment of choice, but other forms of therapy such as radiation and chemotherapy are available.