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Lumps and Bumps on Cats

From time to time, you may notice lumps s 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.

This is why it's a good idea as a cat owner to spend some time either grooming or physically checking your cat over so that you are aware if there are any changes.

Small lumps are known as papules, large lumps are nodules.

Common causes of lumps and bumps on cats:

Abscess - 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.

Cancer - A number of cancers can cause lumps and bumps on cats. Melanomas (skin cancer), injection site sarcoma, sebaceous gland tumour, fibrosarcoma, squamous cell carcinoma, mast cell tumour, basal cell tumour, injection site sarcoma.

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.

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.

Flea allergy dermatitis - This would have to be one of the most common causes of lumps on a cat. They are reasonably fine (around 5mm in diameter). Flea allergy dermatitis is caused by an allergic reaction to the saliva injected into the cat during a bite. Most commonly affected areas are around the neck and the rump.

Hematomas - Ear hematomas are 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.

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.

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

Lipomas - A lipoma is a benign tumour composed of fatty tissue. They are fairly rare, and when they do occur, it's usually in older cats. They are found under the skin, are circular in shape, well defined and firm.

Liposarcomas - These are malignant tumours of fat. Unlike lipomas (above), liposarcomas are poorly defined.

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

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.

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 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. A small tissue sample of the lump is removed and viewed under a microscope.

How are lumps treated?

Treatment is aimed at the cause of the lumps and may include:

  • Abscesses need to be opened up (if they haven't already), drained and cleaned out. Your vet may prescribe a course of antibiotics.
  • Cancer - Surgical removal of the tumour followed by radiation or chemotherapy.
  • Contact dermatitis - Removal or avoidance of the cause. Corticosteroids may be prescribed to control the itching.
  • Flea treatment to remove fleas.
  • Hematomas need to be opened up and drained.
  • 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 will generally go away on their own within a week or two.
  • 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.

Also see:

Scabs on cats   Cat questions   Cat symptoms