Last Updated on June 4, 2021 by Julia Wilson
From time to time, you may notice lumps on your cat which may be singular, or multiple, small or large, firm or soft. Most lumps on cats are harmless, but some can indicate a more serious problem.
You will see the words benign and malignant throughout this article. Benign tumours do not invade nearby tissue or spread to other parts of the body. Malignant tumours (or cancers) may spread to adjacent tissue and other parts of the body.
You may notice different names for these lumps, below is a brief glossary.
- Macule – Flat small lesions
- Papule – Small elevated solid lesion
- Plaque – Large elevated solid lesion
- Nodule – Firm, solid lesions in or under the skin which are greater than 5 mm
- Vesicle – Small fluid-filled blister
- Bullae – Large fluid-filled blister
- Urticaria – Rash of raised, red circular and itchy bumps
- Pustule – Small blister containing pus
- Scabs – Dry, rough crust which forms over a cut or wound
- Ulcers – Open sore
An abscess is a collection of pus. They are usually the result of a cat bite that has become infected. The body sends white blood cells to the area to fight off the bacteria and walls off the area. Pus is a collection of bacteria and white blood cells.
Abscesses are a common injury in entire males who roam due to a higher incidence of territorial fighting.
Symptoms: A painful mass that feels warm to the touch; there may be hair loss and fever. It is possible for the abscess to rupture, in which case a foul-smelling discharge (puss) which may be blood-tinged will erupt from the area.
Location: Anywhere, most commonly head, neck, forelimbs, and base of the tail
Treatment: Lance, flush and pack the area as well as oral antibiotics.
Basal cell tumour
A slow-growing tumour that originates from the cells of the epidermis. Seen most often in middle-aged to senior cats with a higher incidence in Siamese, Himalayan and Persian cats. Over 90% of basal cell tumours are benign.
Symptoms: Firm, solitary and well defined hairless lump which can range in size from 0.2 cm to 10 cm in diameter. Heavy pigmentation of the tumour is common.
Location: Head, neck, and shoulders are the most common locations.
Treatment: Surgery to remove the tumour follow up chemotherapy if the neoplasm is malignant.
Rare, slow-growing, benign (non-cancerous) tumours of the fat cells that are surrounded by a fibrous capsule. Lipomas occur most often in senior cats.
Symptoms: Painless, well defined, soft, round, movable lumps under the skin.
Treatment: Wait and see, if the tumour is impeding movement, surgical removal.
Cutaneous skin horns
Benign growths composed of keratin. Cutaneous skin horns are also associated with FeLV, and papillomavirus infection and affected cats should be tested for FeLV.
Symptoms: Hard, horn-like growths most commonly on the footpad or near the claws. Some cats may experience lameness.
Location: Anywhere but most common on the footpad.
Treatment: If the horns are not causing discomfort, the veterinarian may suggest a wait and see approach. If they are causing pain, they can be surgical removal will be necessary, ensuring the base is removed to prevent re-growth.
Tiny parasitic mites which live in vegetation and cats become infected when roaming an infested area. Chiggers pierce the skin and inject saliva, which contains digestive enzymes to break down the skin layers. They feed on the blood serum (the clear, watery part of the blood).
Symptoms: Intense itching and bumps develop at the site of the bite.
Location: Most often the feet and legs
Treatment: Infection is usually self-limiting, and in most cases no treatment is necessary. In some cases, your veterinarian may prescribe anti-parasitic medication to kill the parasite.
Contact dermatitis is caused by contact with an allergen (allergy-causing agent) or an irritant. This could be plants, chemicals, shampoos etc.
Symptoms: Red and inflamed skin rash with areas of hair loss.
Location: Most common areas with thinner fur such as the face, belly, and inside of the hind legs
Treatment: Removal or avoidance of the cause which may require tests to determine the allergen. Corticosteroids to control itching.
Cowpox is a rare viral infection that can infect cats in Europe. Inoculation from a bite or a scratch is the most common mode of transmission.
Symptoms: A single small macule (small flat lesion) that gradually increases in size which over time becomes a papule (a swollen pimple-like bump).
Location: Most common areas with thinner fur such as the face, belly, and inside of the hind legs
Treatment: Most cases are self-limiting with little treatment other than gently cleansing with antiseptic and antibiotics if a secondary bacterial infection has developed.
Cryptococcosis is a common infectious disease caused by the yeast-like fungus Cryptococcus neoformans, which occurs in areas contaminated with bird (especially pigeon) droppings. Immunocompromised cats are most vulnerable to this disease, and when they do, symptoms are usually more serious.
Symptoms: Infection is limited to the bridge of the nose with swelling to the area for most affected cats. Other symptoms can include sneezing, nasal discharge, ulcerated lesions, nasopharyngeal granulomas, which are fleshy, polyp-like masses that may protrude from the nasal cavity.
Treatment: One of the azole type drugs such as itraconazole to kill the yeast, surgical removal of lesions from the nasal cavity, supportive care such as a feeding tube or intravenous fluids if necessary.
A type of maggot infection caused by several species of botfly found in America and Canada between July and September. Flies lay their eggs near rodent or rabbit burrows. Heat stimulates larvae to hatch from the eggs. Cats become infected when investigating infested areas, where the larvae attach to the fur before they enter the body via the mouth, nostrils or a wound. They remain localised for 6-8 days before migrating through the trachea, thoracic and abdominal cavities to a subcutaneous location (commonly the head, neck, and trunk) where it sets up home, feeding on surrounding tissue.
Symptoms: A painful warble (swelling) up to one inch long with a fistula (breathing hole) in the centre, it may be possible to see the head of the parasite in the hole. The cat may bite and lick the area. In some cases, the larvae can migrate to the brain and cause neurological disturbances.
Location: Anywhere, but the head and nose are the most common sites.
Treatment: Surgical removal of the larvae.
Blackheads on the cat’s chin and lips due to blocked sebaceous glands there are several causes which include the use of plastic food bowls, hormonal imbalances, allergies, overactive sebaceous glands and poor grooming.
Symptoms: Blackheads (comedones), redness and inflammation, can develop in some cats and in severe cases, painful nodules with draining lesions can develop.
Location: Chin and lips
Treatment: Clean the area daily with witch hazel for mild acne. Severe acne will require medicated ointment and in some cases, antibiotics.
Flea allergy dermatitis
One of the most common causes of lumps on a cat which are small in size and feel dry and gritty (miliary dermatitis). Flea allergy dermatitis is the result of an allergic reaction to the saliva injected into the cat during a bite. Just one flea is enough to trigger flea allergy dermatitis.
Symptoms: Miliary dermatitis (small, firm, scabs) along the back close to the base of the tail, and the neck. As the back hard for the cat to reach, self-trauma is limited, however large oozing scabs can develop on the neck due to constant scratching to relieve itching.
Location: Most commonly, the neck and on the back towards the tail.
Treatment: Diligent flea control and corticosteroids for severely affected cats to reduce itching.
Symptoms: The affected ear will feel soft, warm and painful.
Treatment: Surgery to open and drain the hematoma, the skin is then stapled back in place to prevent the hematoma from re-forming.
Rare but aggressive tumours which originate from the endothelial cells which line the inner surface of the blood vessels. This cancer can invade several organs, including the spleen, liver, and heart.
Symptoms: Multiple masses which are firm, raised and dark. Bruising may also be present.
Location: Most common on the rear legs, abdomen, and prepuce (fold of skin surrounding the penis).
Treatment: Surgery to remove the tumour followed by chemotherapy.
This rare fungal infection is present in the environment. Cats become infected when they inhale or ingest the fungus, once inside the body, it becomes a yeast. The lungs are the most commonly affected, although infection can spread (disseminate) to other parts of the body.
Symptoms: If the skin is involved, multiple papules (small lesions) and nodules (large lesions) develop.
Location: Most commonly on the head and neck.
Treatment: Mild cases may not require treatment. However, severe cases will need antifungal drugs such as itraconazole for several months. Severely sick cats may require hospitalisation and supportive care, such as fluids and nutritional support.
Injection site granulomas
Lumps found beneath the skin after a vaccination. They will generally go away on their own within a few days or weeks. However, you must keep an eye on the lump and if it doesn’t go away reasonably quickly, or if it grows in size, seek veterinary attention.
Symptoms: Small, mobile, firm, painless lump at the site of the injection.
Location: Back of neck or limb where injection occurred.
Treatment: No treatment is necessary; they will generally go away on their own within a week or two. If they don’t go away, or if they increase in size, see a veterinarian as it could be an injection site sarcoma, which is life-threatening.
Injection site sarcoma
Also known as vaccine-associated sarcoma (VAS) this aggressive cancer can develop at the site of vaccination. The cause is still not fully understood, but it is believed to be related to the adjuvant in the vaccine, which is there to stimulate the cat’s immune response to the area. Fibrosarcomas are the most common type of tumour involved.
Symptoms: Firm swelling under the skin at the site of the injection, there may also be ulceration.
Location: Back of the neck or limb where injection occurred.
Treatment: Surgical excision or amputation if a limb is affected. Chemotherapy may be necessary if it is not possible to remove the entire tumour.
Insect bite or sting
Any number of insects can bite or sting the curious cat. Most stings are self-limiting; however, some insects can be poisonous.
Symptoms: Small, red lump, itchiness, pain, and tenderness.
Treatment: These should resolve in a day or two. Keep an eye on the area for signs of infection. Apply topical iodine to the area. Antihistamines and ice can relieve swelling and itching.
Malignant (cancerous) slow-growing, non-painful tumours of fat tissue. Feline leukemia virus has been linked to liposarcomas.
Symptoms: Firm nodules under the skin which can grow up to 2 cm in diameter.
Location: The legs are the most common location.
Treatment: Surgical removal of the tumour and radiation therapy as a follow up in some cases where a wide margin is not possible.
Mammary (breast) tumour
Benign and cancerous tumours of the breasts, 80-90% of mammary tumours are malignant (cancerous).
Symptoms: Painless, firm, nodular mass on one or more mammary glands. Ulceration may occur.
Location: Nipples and breasts (male and female).
Treatment: Surgical excision of the tumour as well as any affected lymph nodes (if the tumour is malignant). Chemotherapy may be necessary if the cancerous tumour can’t be removed, or was only partially removed.
Mast cell tumour
Benign or cancerous tumours which arise from mast cells (a type of white blood cell). Mast cells are the second most common skin tumour in cats, and approximately 10% of tumours are cancerous. There is a higher incidence in Siamese cats, which suggests a genetic component.
Symptoms: Small, firm and raised hairless lumps, some can be quite itchy to the cat. There is a higher incidence in Siamese cats.
Location: Head, neck, and body.
Treatment: Surgical excision of the tumour. Chemotherapy may also be necessary.
Melanomas are an aggressive tumour which arises from the cells which produce pigment (melanocytes).
Symptoms: Pigmented or non-pigmented solid growths seen most often in middle-aged to senior cats.
Location: Skin (most commonly face, trunk and feet) and oral cavity.
Treatment: Surgical removal of the tumour and chemotherapy as a follow-up if it is not possible to remove the entire tumour.
Inflammation of the fat under the skin may be caused by infection, immune-mediated, trauma, bite wounds, steroid treatment and diseases of the internal organs.
Symptoms: Lumps and bumps which are easily movable under the skin which may be soft or firm and often painful. They can range in size from a few mm to several cms in diameter.
Treatment: Treat the underlying cause if one is found. Immunosuppressive drugs may be prescribed.
A frustrating autoimmune condition characterised by the presence of small fluid-filled pustules which eventually break open forming dry crusts. There are three types of pemphigus, each affecting different parts of the body. The most common is pemphigus foliaceus, which starts around the eyes before spreading to the ears, neck, nail beds, footpads, nipples, and groin. Pemphigus erythematosus affects the feet only and pemphigus vulgaris, affects the deeper layers of the skin producing the most severe symptoms affecting the mouth, claw folds, armpits, and groin. Vesicles easily rupture and form deep, painful ulcers.
Symptoms: Fluid-filled pustules which eventually break open and then form a dry crust. Symptoms may wax and wane over time.
Location: Multiple areas.
Treatment: Immunosuppressive drugs. Initially, a high dose will be administered, and when the condition is under control, this will be slowly tapered to the lowest dose possible to maintain remission.
Inflammatory lesions commonly found on the mouth, face, and skin of cats. The lip is by far the most common location. The cause is still unknown but may be associated with dental infection or flea allergies.
Symptoms: Raised, thick, brown ulcer which is well defined and glistening in appearance. The top lip is the most common location of these ulcers.
Location: Most commonly on the mouth and lips.
Treatment: Avoid the cause where possible. Your veterinarian can prescribe steroids to reduce inflammation and immune-suppressing drugs if the previous methods fail to obtain results.
Cysts are fluid-filled sacs that arise from the sebaceous glands beneath the skin. They are less common in cats than they are in dogs and can occur on any part of the body.
Symptoms: Painless, smooth, soft fluid-filled lumps which may have a blue hue to them. Cysts can grow up to 1-2 inches in diameter.
Location: The most common locations are the head, neck and trunk.
Treatment: Your veterinarian may decide to leave the cyst if it’s not bothering your cat or surgically remove it.
Sebaceous gland tumour
Fluid-filled sacs form from the sebaceous glands under the skin. They are less common in cats than they are in dogs and can occur on any part of the body.
Symptoms: Polyp-like mass with a narrow base which is 2-5 mm in diameter. Sebaceous gland tumours are often itchy, which can result in self-trauma and secondary infection.
Location: Anywhere, but most commonly the head.
Treatment: Surgery to remove the tumour. Chemotherapy as a follow up if the tumour is malignant.
Squamous cell carcinoma
This common cancer can often arise from excessive exposure to the sun; white and light coloured cats are at increased risk squamous cell carcinomas are slow to spread, but if ignored, they can invade local lymph nodes and spread to the lungs.
Symptoms: Small raised red dots on the affected area, which slowly increase in size into scaly red patches which crust and bleed, non-healing sores and scabs along the ear margins.
Location: Most commonly the ears and nose
Treatment: Surgical removal or cryosurgery to remove the cancerous tissue followed by chemotherapy.
Ticks are ectoparasites (parasites that live on the outside of the body). Several ticks can affect cats. Ixodes holocyclus is the most common tick in Australia which can kill a cat when it injects neurotoxins into the cat as it feeds. Ticks bury their head into the skin of their host (your cat), and you may see or feel the body of the tick on the skin.
Symptoms: Drooling, change in vocalisation, coughing, panting, dilated pupils, limb weakness, incontinence, laboured breathing, blue-tinged gums and coma.
Treatment: Removal of the tick. If the cat has been bitten by a paralysis tick, emergency veterinary care will be necessary. This will include antiserum which contains antibodies against the neurotoxin, as well as aggressive supportive care.
An umbilical hernia is an opening in the abdominal wall at the site of the umbilicus. This opening is present in the unborn kitten’s abdomen but should close shortly after birth. In some kittens, this doesn’t happen, and the opening remains, the size of which can vary from 5 mm to 18 mm.
Symptoms: The skin covers a hernia, however sometimes abdominal fat and the underlying organs can push through the opening, especially with larger hernias. It may be possible to push the contents back into the abdomen, however in some cases, they become adhered to the skin and become trapped. This is a medical emergency. You may notice a soft round mass at the belly button if the abdominal contents are protruding this will feel firm.
Location: Umbilicus (belly).
Treatment: If a hernia hasn’t resolved on its own, surgery will be necessary. This can, at the same time, as your cat’s spay/neuter surgery.
A skin rash with many possible causes such as medications, chemicals, food allergies, pollens, plants and flea collars.
Symptoms: Small, red and itchy bumps. Depending on the allergen involved, symptoms may be seasonal or non-seasonal.
Treatment: Avoid the allergen if possible, antihistamines or cortisone to relieve symptoms.
See a veterinarian if your cat has a lump that is larger than a pea and has been there for a month or more.
Sometimes the veterinarian can give a tentative diagnosis during the examination. Lumps from abscesses for example or flea allergy dermatitis and umbilical hernias are very easy to diagnose based on symptoms alone.
- When did you notice the lump(s)/how long has the cat had the lump(s)?
- Have you noticed any other symptoms such as weight loss, diarrhea, vomiting, loss of appetite, pain, etc.?
- Has the lump changed in size or stayed the same?
- Fine needle aspirate and cytology – A small sample of the lump is removed via needle for microscopic evaluation of the cells (cytology).
- Diagnostic imaging – To evaluate internal lumps, such as inside the nasal cavity.
- Histopathology – Surgical removal of tumours over 1 cm. Tumours over 1 cm will be surgically excised and sent to a laboratory for histopathology (examination of the tissue sample to determine the type of cells and if they are malignant or benign).