Lip ulcer in catseosinophilic granuloma or a problem in the mouth?

What is eosinophilic granuloma in cats?

The eosinophilic granuloma complex is not a single disease but a group of similar reactions of the skin and the lining of the mouth in cats. The name comes from eosinophils — a type of white blood cell involved in allergic reactions. They gather in the tissue, and an ulcer, a plaque or a firm nodule appears there.

Put simply, it is the way a cat's body responds to an irritant. So the words “eosinophilic granuloma” describe the type of lesion, not why it developed. Three forms are usually described:

• indolent ulcer (rodent ulcer) — an ulcer on the upper lip;
• eosinophilic granuloma — firm nodules or swellings: in the mouth, on the chin, on the lower lip, or linear lesions on the back of the thighs;
• eosinophilic plaque — itchy, red, moist patches of skin, most often on the belly and inner thighs.

One cat can have several forms at the same time, and lesions may shrink and then come back.

What a lip ulcer and granulomas in the mouth look like

Owners usually come in when they notice one of these:

• an ulcer on the edge of the upper lip — under the nose near the midline or opposite the lower canine. It is well defined, with raised edges, red-brown or yellowish, on one or both sides. Without treatment it can enlarge and erode the lip tissue;
• a swollen lower lip or chin — a soft or firm swelling without an obvious wound;
• yellowish or pink nodules on the tongue or palate — sometimes ulcerated on the surface; the cat may drool, eat cautiously or have bad breath;
• skin changes — scratch marks, plaques on the belly, linear lesions on the thighs, overgrooming.

An indolent ulcer is usually not itchy and the cat behaves as usual, which is why it is often noticed late. Granulomas in the mouth are more bothersome but are easily confused with other causes of inflammation: which diseases cause a red mouth and ulcers is covered on the page red mouth or ulcers in a cat.

Why a lip ulcer must be told apart from problems in the mouth

A vet can often suspect an eosinophilic lesion from its appearance. But the lip borders the oral cavity, and several dental problems produce a very similar picture:

• Chronic gingivostomatitis. The inflammation spreads beyond the gums — to the back of the mouth, the palate and the lining of the lips; lesions can be ulcerated or cobblestone-like and are very painful. How it is recognised and treated is explained in the article on stomatitis in cats.
• Trauma from a tooth. The sharp edge of a fractured tooth, or a lower canine that presses into the upper lip after the upper canine has been lost or because it has shifted, keeps injuring the tissue, and the wound will not heal while the cause remains. A fractured tooth with an exposed pulp can lead to an abscess at the root — then the lip, chin or the area under the eye swells.
• Tooth resorption (TR). Over the tooth defect the gum becomes red and overgrown, and once the crown breaks down, roots and sharp fragments are left behind. Around the canines and premolars this can be mistaken for a granuloma, and the full picture is only visible on radiographs — see the article on tooth resorption in cats.
• Oral tumours. Squamous cell carcinoma is the most common malignant oral tumour in cats. It can look like an ulcer that does not heal or a swelling on the gums, the lip or under the tongue, and nearby teeth may become loose. Which masses occur in the mouth and why they cannot be judged from photos is covered on the page growth or mass on the gums.

Individual signs can point in a direction, but none of them makes a diagnosis:

What a veterinary dentist does

If the ulcer is typical and no other changes are seen in the mouth at the consultation, anaesthesia may not be needed: the lesion is assessed and treatment is prescribed without it. But if there are signs of problems in the mouth or the lesion behaves unexpectedly, my job is to examine the whole oral cavity and find or rule out a dental cause.

A complete examination of a cat's mouth, probing every tooth and full-mouth dental radiography are only possible under anaesthesia, which is given and monitored by a separate veterinary anaesthetist. Radiographs show what the eye cannot see: roots of fractured teeth, resorption under the gums and changes in the bone next to the lesion. How dental care for cats is organised in general is described on the page cat dentistry.

1. 01

   Consultation

   I examine the lip, the mouth (as far as the cat allows) and the skin, and ask which medicines have already been given and how the lesion has changed.

2. 02

   Pre-anaesthetic tests

   Blood tests and other investigations — the list is decided individually, when clinically indicated.

3. 03

   Oral examination under anaesthesia

   Examination and probing of every tooth as part of COHAT, with full-mouth dental radiography.

4. 04

   Biopsy

   If the lesion is atypical, I take a tissue sample for histopathology.

5. 05

   Treatment and plan

   I treat or extract teeth that injure the lip or keep the inflammation going; then a shared plan with the cat's regular vet or a dermatologist.

When a biopsy is needed

A biopsy means taking a small piece of tissue for histopathology. The pathologist assesses the structure of the tissue and can tell eosinophilic inflammation from a tumour or an infection. On the lip and in the mouth it is taken under anaesthesia. I recommend not putting off a biopsy if the lesion does not behave as expected:

• it does not shrink after several weeks of treatment prescribed by a vet;
• it quickly comes back once the medicine is stopped;
• it grows, bleeds, becomes firm or fixed to the bone;
• it appeared in an older cat, especially as a single lesion on one side;
• it is on the gums, under the tongue or at the back of the mouth;
• nearby teeth are loose or the bone looks changed on radiographs.

An impression smear (cytology) sometimes helps but does not always answer the question. How cytology differs from histopathology and why the biopsy plan is decided before a mass is removed is explained in the article on diagnosing gum growths. How I take biopsies and remove masses in the mouth is described on the page oral masses.

Causes, treatment and who manages the allergy

The eosinophilic complex is often linked to allergy. Possible causes include:

• flea allergy — even if you see no fleas: cats groom them away very thoroughly;
• food allergy — to certain proteins in the diet;
• environmental allergy — to pollen or house dust mites;
• a reaction to insect bites, such as mosquito bites.

In some cats no cause is found. To be honest: I do not treat allergies. The search for an allergy (thorough flea control for every pet in the household, an elimination diet that lasts for weeks) and long-term treatment are usually planned together with a veterinary dermatologist or your cat's regular vet. My part is to rule out causes in the mouth, take a biopsy if one is needed and treat teeth that injure the lip or keep the inflammation going.

The ulcer or granuloma itself is treated with anti-inflammatory or immunomodulating medicines, most often steroids, and, when clinically indicated, with an antibiotic if a bacterial infection has set in. The vet chooses the course, and it usually lasts weeks rather than days. In many cats the lesions can be kept under control for a long time, but relapses are possible, especially if the cause remains.

Long or repeated courses of steroids, including long-acting injections, can have serious side effects in cats, such as an increased risk of diabetes. So every new course is a reason to review the diagnosis, not to repeat “what we did last time”.

What affects the cost

The cost depends on what your cat actually needs: a consultation, pre-anaesthetic tests, anaesthesia, an oral examination and radiographs as part of COHAT, a biopsy and histopathology, and treatment or extraction of teeth. The exact scope becomes clear after the examination, and the final amount after dental radiographs.

Frequently asked questions