(Mouth cancer and cancer of the pharynx)

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Note for Pet Owners:
If your pet develops a swelling or growth in it's mouth seek the advice of your veterinary surgeon.

Topics on this Page:

Cancers which occur in the mouth or in the region of the pharynx (at the back of the mouth) can be either
malignant or benign. Some forms of malignant cancer in this region (e.g. melanoma) are extremely serious, spread rapidly and can be life threatening. Others are not serious at all, although they can cause alarm to an owner (e.g. oral papillomatosis - warts). As with all tumours early accurate diagnosis is important so that appropriate treatment can be started as soon as possible.

The most common malignant cancers to occur in the mouth or pharynx of the dog are melanomas, squamous cell carcinomas and fibrosarcomas. The first two can be very serious and malignant melanomas in particular can spread (called metastatic spread or metastasis) very rapidly to other organs such as regional lymph nodes and the lungs. Melanomas are more common in the
Chow-Chow and Great Dane and unfortunately carry a poor prognosis.

Fibrosarcomas are seen in younger dogs and rarely spread but they frequently recur locally after treatment.

Epulides are benign and, although they can grow to be quite large, present problems with eating, and sometimes ulcerate and bleed they are not life threatening. Epulides are cauliflower-type fibrous growths which occur along the gum margin (hence they are called "gingival cancer", and they are sometimes called periodontal fibrous hyperplasia). They are common in brachycephalic (short-nosed) breeds of dog, especially the Boxer and English Bulldog.

In general cancers occur more frequently with advancing age.

Young dogs, however, frequently develop warts in the mouth and on the tongue and these are cause by papilloma virus and the warts themselves are benign.. The warts can affect eating and sometimes localised secondary infection can occur giving a foul smell on the breath, but the disease is not serious and is self-limiting, lasting only about 6-12 weeks.

In cats about 50% of cancers in the mouth involve the tongue, and the most common oropharyngeal cancer is squamous cell carcinoma.

The signs associated with oropharyngeal cancers will vary depending upon the site of the tumour and the type of cancer. Typical signs are :

  • Difficulty or pain when eating or swallowing
  • Bad breath (halitosis)
  • Bleeding from the gums or tumour mass
  • Ulcers in the mouth
  • Development of abnormal growths in the oral cavity or pharynx - including the tonsilar crypt.

Sometimes diagnosis can be made based upon the typical appearance of the cancer, the history and presenting signs. A black pigmented, ulcerated bleeding tumour that has appeared and grown very quickly in the mouth of an ageing Chow-Chow is likely to be a malignant melanoma, whereas multiple small cauliflower-type growth in the mouth of a young puppy are most likely papillomas.

In other cases the type of tumour-type will not be obvious and accurate diagnosis will rely on histological examination of a biopsy, or removed tumour.

In all cases it is important to examine local lymph nodes in the throat or neck to detect evidence of spread. Enlargement or pain can be detected by feeling the site, but an Xray of the neck may be needed to identify retropharyngeal spread. An enlarged retropharyngeal lymph node is seen as a large soft tissue mass under the cervical spine, often displacing the windpipe (trachea) and gullet (oesophagus).

A chest Xray is very important to ensure that spread to the lungs has not occurred.

Any evidence of spread is a poor prognostic indicator which may affect the method(s) of treatment used. Ensuring a satisfactory quality of life is often more important than prolonging life in patients with advanced metastatic disease.

There are a wide range of treatment possibilities from
surgical excision for benign, well localised cancers, to chemotherapy, radiotherapy and hyperthermia for malignant cancers.

Excision is recommended for benign cancers - e.g. warts, and epulides - though the latter frequently recur.

Radiotherapy is recommended for oral squamous cell carcinomas and the prognosis is good.

Squamous cell carcinoma of the tonsil in older dogs however, is a much more serious form of cancer because it often spreads to the retopharyngeal lymph nodes and frequently spreads further to the lungs.

Combination therapies are usually advocated for the malignant tumours.