Lumps and Bumps on Cats-Causes, Symptoms & Treatment

Common causes of lumps and bumps              Diagnosing the cause of lumps

lumps and bumps on cat

From time to time, you may notice lumps on your cat. They 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 tumors do not invade nearby tissue or spread to other parts of the body. Malignant tumors (or cancers) may spread to nearby tissue and to 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

Common causes of lumps and bumps on cats:


An abscess is a collection of pus. They are usually the result of a cat bite which 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. An abscess can range in size, the ones I’ve encountered were around the size of a marble. You may notice the area feels hot and is painful to the cat and there is hair loss. Common areas affected are around the head and neck and base of the tale. Entire males are more frequent in entire males.

Location: Anywhere, most commonly head, neck, and forelimbs

Treatment: Lance, flush and pack the area as well as oral antibiotics.

Basal cell tumor

A slow-growing tumor which originates from the cells of the epidermis. Seen most often in middle-aged to senior cats. Pigmentation is common in these tumors. Over 90% of basal cell tumors are benign.

Location: Anywhere.

Basal cell tumur: Surgery to remove the tumor, follow up chemotherapy if the tumor is malignant.

Benign skin growth

Lipomas: A rare, benign skin growth. They are found under the skin and are well defined, circular and firm.

Cutaneous skin horns: Benign growths composed of keratin, they are most commonly found on the cat’s footpad and are 1-4 cm in length and hard/horn-like.

Location: Anywhere.

Treatment: Surgical removal if necessary. Radiation treatment may be necessary as a follow-up treatment.


Tiny parasitic mites which live in vegetation. 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 blood). 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 a suitable anti-parasitic medication to kill the parasite.

Contact dermatitis

Contact dermatitis is caused by contact with an allergen (allergy-causing agent) or an irritant. This could be plants, chemicals, shampoos etc.

Location: Most common areas with thinner fur such as the face, belly, and inside of the hind legs

Contact dermatitis: Removal or avoidance of the cause. Corticosteroids to control pruritis.


A rare viral infection which can infect cats in Europe. Inoculation from a bite or a scratch is the most common mode of transmission. Symptoms begin with a single small macule which 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.


A common fungal infection which is found in the environment. Cats become infected by inhaling spores, immunocompromised cats are most vulnerable to this disease and when they do, symptoms are usually more serious. In most cats, infection is limited to the bridge of the nose. Other symptoms may include sneezing, nasal discharge, ulcerated lesions, nasopharyngeal granulomas which are fleshy, polyp-like masses which may protrude from the nasal cavity.

Location: Nose

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 a number of 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 localized 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. A warble forms with a fistula (breathing hole) in the skin. In some cases, the larvae can migrate to the brain causing neurological disturbances.

Location: Anywhere, but the head and nose are the most common sights.

Treatment: Surgical removal of the larvae.

Feline acne

Blackheads on the cat’s chin and lips due to blocked sebaceous glands. You may notice a number of dirty looking black spots on your cat’s chin. Some cats are more susceptible than others.

Location: Chin

Flea allergy dermatitis

One of the most common causes of lumps on a cat. They are small in size and feel dry and gritty. Flea allergy dermatitis is caused by an allergic reaction to the saliva injected into the cat during a bite. Just one flea is enough to trigger flea allergy dermatitis.

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.

Ear hematomas

Blood filled pockets of the ear which are usually caused by trauma from scratching. The affected ear will feel soft, warm and painful.

Location: Ears.

Treatment: Surgery to open and drain the hematoma, the skin is then stapled back in place to prevent the hematoma reforming.


Rare but aggressive tumors which originate from the endothelial cells which line the inner surface of the blood vessels. This cancer can invade a number of organs including the spleen, liver, and heart. When the skin is affected firm nodules can be felt under the skin. There may be a single or multiple masses which are firm, raised and dark. Bruising may be seen in the masses.

Location: Most commonly found on the rear legs, abdomen, and prepuce (fold of skin surrounding the penis).

Treatment: Surgery to remove the tumor followed by chemotherapy.


This rare fungal infection can be found 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. If the skin is involved, papules (small lesions) and nodules (large lesions) develop.

Location: Most commonly on the head and neck.

Treatment: Mild cases may not require treatment. More serious cases may require antifungal drugs such as itraconazole which will be prescribed for several months. Severely sick cats may require hospitalization and supportive care such as fluids and nutritional support.

Injection site granulomas

These are lumps found beneath the skin after a vaccination has been administered. They will generally go away on their own within a few days or weeks, however, it is important you keep an eye on the lump and if it doesn’t go away reasonably quickly, or if it grows in size, seek veterinary attention.

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 a 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 tumur involved.

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 the tumur can’t be removed, or was only partially removed.

Insect bite or sting

Any number of insects can bite or sting the curious cat. You may notice a lump, itchiness, pain, and tenderness.

Location: Anywhere

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 to control itching.


These are malignant tumors of fat underneath the skin.

Location: Anywhere

Mammary cancer

Painless, firm, nodular mass on one or more mammary glands. Ulceration may occur.

Location: Nipples and breasts (male and female).

Treatment: Surgical excision of cancer as well as any affected lymph nodes. Chemotherapy may be necessary if the tumur can’t be removed, or was only partially removed.

Mast cell tumur

Arising from mast cells, which are a type of white blood cell. Mast cell tumurs can be benign or cancerous account for approximately 20% of skin masses. Mast cell tumurs are small, firm and raised lumps which are hairless, 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 tumur. Chemotherapy may also be necessary.


An aggressive tumor which arises from the cells which produce pigment (melanocytes). 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 tumor. Chemotherapy may be necessary if the tumor can’t be removed, or was only partially removed.


This rare condition is caused by inflammation of the fat under the skin which may be caused by infection, trauma, bite wounds, steroid treatment and diseases of the internal organs. Lumps and bumps can be felt on the skin which may be soft or firm and often painful.

Location: Abdomen.

Treatment: Treat the underlying cause if one is found. Immunosuppressive drugs may be prescribed.


A frustrating autoimmune condition characterized 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, foot pads, 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.

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.

Rodent ulcer

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. They are raised, thickened, 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 may prescribe steroids to reduce inflammation and immune-suppressing drugs if the previous methods fail to obtain results.

Sebaceous cysts

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. Sebaceous cysts feel like a marble under the skin.

Location: Anywhere.

Treatment: Your veterinarian may decide to leave the cyst if it’s not bothering your cat or surgically remove it.

Sebaceous gland tumor

Fluid-filled sacs which 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. They feel like a marble under the skin.

Location: Anywhere, but most commonly the head.

Treatment: Surgery to remove the tumor. Chemotherapy as a follow up if the tumor is malignant.

Squamous cell carcinoma

This common cancer can often arise from excessive exposure to the sun, white and light coloured cats are at greatest risk. These cancers are slow to spread but if ignored they can invade local lymph nodes and spread to the lungs. Symptoms include lesions which don’t heal, a red spot or a crusty lesion.

Location: Most commonly the ears and nose

Treatment: Surgical removal or cryosurgery to remove the cancerous tissue followed by chemotherapy.


Ticks are ectoparasites,  parasites which live on the outside the body. There are a number of ticks which can affect cats, the most common in Australia is the paralysis tick, which can kill a cat. 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.  Signs of tick poisoning include drooling, change in vocalization, coughing, panting, dilated pupils, limb weakness, incontinence, labored breathing, blue-tinged gums and coma.

Location: Anywhere

Treatment: Removal of the tick and follow up veterinary attention.

Umbilical hernia

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. 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 of your cat’s spay/neuter surgery.

Urticaria (hives)

An allergic reaction characterized by the presence of small, red and itchy bumps. There are many possible causes of urticaria including medications, chemicals, food allergies, pollens, plants and flea collars. Depending on the allergen involved, symptoms may be seasonal or non-seasonal.

Location: Anywhere

Treatment:  Removal of the allergen if possible, antihistamines or cortisone can be given to relieve symptoms.


In many cases, your veterinarian can diagnose the problem upon physical examination. Lumps from abscesses for example or flea allergy dermatitis and umbilical hernias are very easy to diagnose based on symptoms alone. He will obtain a history from you and may ask the following questions:

  • 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?

Diagnostic tests:

  • Fine needle aspirate.
  • Biopsy and histopathology of tissue samples as well as cytology of any discharge from the affected area.
  • Diagnostic imaging where the lump is internal (such as inside the nose).
  • Surgical removal of tumors over 1 cm. Your veterinarian will send the tissue to a laboratory to determine if the lump is benign or malignant.

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