Lumps and Bumps on Cats

Common causes of lumps and bumps    Diagnosing the cause of lumps   How are lumps treated?

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 tumours do not invade nearby tissue or spread to other parts of the body. Malignant tumours (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. You will notice that lesions are used interchangably with lumps or bumps. Lesions are a broad term for wounds, sores, lumps and tumours.

  • 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 most commonly affected.

Location: Anywhere, most commonly head, neck and forelimbs

Basal cell tumour

A slow growing tumour which originates from the cells of the epidermis. Seen most often in middle aged to senior cats. Tumours are often pigmented. Over 90% of basal cell tumours are benign.

Location: Anywhere.

Benign skin growth

Lipomas are rare, benign skin growths which are seen most common on older cats. They are found under the skin and are well defined, circular and firm. Cutaneous skin horns are 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.


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

Contact dermatitis

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

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


A rare viral infection which can infect cats in Europe. The most common mode of transmission is via inoculation from the bite or scratch of an infected animal. Symptoms begin with a single small macule which gradually increases in size which over time becomes a papule (swollen pimple like bump).

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


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 usually limited to the nose where a swelling or mass may develop over the bridge of the nose, other symptoms may include sneezing, nasal discharge, ulcerated lesions, nasalpharyngal granulmonas which are fleshy, polyp like masses which may protrude from the nasal cavity.

Location: Nose

Feline acne

Feline acne is caused by blackheads forming on the chin 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

This would have to be 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.

Location: Most commonly the neck and on the back towards the tail

Ear hematomas

Blood filled pockets of the ear. They are usually caused by trauma or scratching (generally from ear mites). The affected ear will feel soft, warm and painful.

Location: Ears


Rare but aggressive tumours which originate from the endothilial 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 on the masses.

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


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

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

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 tumour involved.

Location: Back of the neck or limb where injection occurred

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


These are malignant tumours of fat underneath the skin. Unlike lipomas (above), liposarcomas are poorly defined.

Location: Anywhere

Mammary cancer

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

Location: Nipples and breasts (male and female)

Mast cell tumour

Arising from mast cells, which are a type of white blood cell the skin or the internal organs can be affected. Cutaneous mast cell tumours account for approximately 20% of skin masses in cats although the majority of them are benign. Mast cell tumours 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


An aggressive tumour 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


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


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, 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

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. Females are far more commonly affected than males.

Location: Most commonly on the mouth and lips

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. They can occur on any part of the body. They feel like a marble under the skin.

Location: Anywhere

Sebaceous gland tumour

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. They can occur on any part of the body. They feel like a marble under the skin.

Location: Anywhere, but most commonly the head

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. There will be hair loss on the affected area.

Location: Most commonly the ears and nose


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. Ticks should be carefully removed so that the head isn’t left in the body. Signs of tick poisoning include drooling, change in vocalisation, coughing, panting, dilated pupils, limb weakness, incontinence, laboured breathing, blue tinged gums and coma.

Location: Anywhere

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 the hernia, however sometimes abdominal fat and the underlying organs can push through the opening, especially with larger hernias. Often the contents can be pushed back into the abdomen, but sometimes they become adhered to the skin or become trapped, which is an 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)

Urticaria (hives)

An allergic reaction characterised 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

How is the cause of lumps diagnosed?

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?

If the cause of the lump(s) isn’t known, he may choose to perform further tests. These may include:

  • Fine needle aspirate. A needle is inserted into the lump and a sample is taken and looked at under a microscope.
  • Biopsy and histopathology of tissue samples. These may be taken under local or general anesthetic.
  • Cytology of any discharge from the affected area.
  • Diagnostic imaging where the lump is internal (such as inside the nose).
  • Tumours (especially those over 1 cm) should be surgically removed and sent to pathology to determine if it is benign or malignant.

How are lumps treated?

  • Abscesses need to be opened up (if they haven’t already), drained and cleaned out. Your vet may prescribe a course of antibiotics.
  • Basal cell tumour – Surgery to remove the tumour, chemotherapy if it is found to be malignant.
  • Chiggers – 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 – Removal or avoidance of the cause. Corticosteroids may be prescribed to control the itching.
  • Cowpox – Most cases are self limiting with little treatment other than gently cleansing with antiseptic and antibiotics if a secondary bacterial infection has developed.
  • Cryptococcosis – One of the azole type drugs such as itraconzole to kill the yeast, surgical removal of lesions from the nasal cavity, supportive care such as a feeding tube or intravenous fluids if necessary.
    Itraconazole, fluconazole or ketoconazole
  • Fleas – Treat your cat with an anti-flea treatment and also treat the environment with an appropriate insecticide.
  • Histoplasmosis – 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 hospitalisation and supportive care such as fluids and nutritional support.
  • Ear hematomas – Surgery to open and drain the hematoma, the skin is then stapled back in place to prevent the hematoma redeveloping.
  • Hemangiosarcoma – Surgery to remove the tumour followed by chemotherapy.
  • Injection site sarcoma – Surgical excision or amputation if a limb is affected. Chemotherapy may be necessary if the tumour can’t be removed, or was only partially removed.
  • Lipomas and liposarcomas need to be surgically removed. Radiation treatment may also be required if the entire tumour can not be surgically removed.
  • Injection site knots – No treatment is necessary, they will generally go away on their own within a week or two.
  • Mammary cancer – Surgical excision of the cancer as well as any affected lymph nodes. Chemotherapy may be necessary if the tumour can’t be removed, or was only partially removed.
  • Mast cell tumour – Surgical excision of the tumour. Chemotherapy may also be necessary.
  • Melanoma – Surgical removal of the tumour. Chemotherapy may be necessary if the tumour can’t be removed, or was only partially removed.
  • Panniculitis – Treating the underlying cause if one is found. Immunosuppressive drugs may be prescribed.
  • Pemphigus – Immunosuppressive drugs will be prescribed to treat this. 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 – Avoidance of the cause (such as parasites) if it is known. Your veterinarian may prescribe steroids to reduce inflammation and immune suppressing drugs if the previous methods fail to obtain results.
  • Sebaceous cysts – Your veterinarian may decide to leave the cyst if it’s not bothering your cat or surgically remove it.
  • Sebaceous gland tumour – Surgical removal, if a malignancy is detected chemotherapy may given after surgery.
  • Squamous cell carcinoma – Surgical removal or cryosurgery to remove the cancerous tissue followed by chemotherapy.
  • Insect bite or sting – These should resolve in a day or two. Keep an eye on the area for signs of infection. Topical betadine can be applied to the area. Antihistamines may be prescribed to control itching.
  • Cutaneous horns – Surgical removal is necessary.
  • Ticks – Removal of the tick. Seek veterinary attention if you suspect your cat has been bitten by a tick as they inject an endotoxin into the cat which can be fatal.
  • Umbilical hernia – If the hernia hasn’t resolved by six months of age surgery will be required to correct it. This can be done at the same time of your cat’s spay/neuter surgery.
  • Urticaria – Removal of the allergen if possible. Antihistamines or cortisone may be recommended to relieve symptoms.

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