Head and neck cancer refers to a group of biological cancers which originate in the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx and larynx. Unfortunately, in man, 90% of head and neck cancers are aggressive squamous cell carcinomas (SCC). Dogs and cats, however, have a much greater variety of cancers affecting the head and neck, but many can still be aggressive and very difficult to treat. David Argyle led last week’s Platinum Member’s webinar and delivered an overview of the many types of cancers encountered in the head and neck of both dogs and cats, and offered advice on how best to manage these often challenging tumours.

David chose to start with oropharyngeal tumours in both cats and dogs with the highly malignant SCC accounting for 70% of oropharyngeal tumour cases in cats. In humans, there has been an association between SCC and human papilloma virus and although there is no clear link to a virus in cats, David explained there is mounting evidence to indicate this may be the case. Oropharyngeal tumours in dogs account for 6% of all canine tumours with melanomas being most commonly encountered (30-40% of all oropharyngeal tumours) followed by SCC (20-30%), then fibrosarcomas (10-20%) and finally dental tumours including epulis (5%).

Clinical signs associated with oropharyngeal tumours include halitosis, decreased appetite, tooth loss, the presence of blood on food or saliva, dysphagia and painful mastication. Enlarged submandibular and/or prescapular lymph nodes may also be observed and David advised if this is observed where no other clinical signs are seen, it is imperative to examine the mouth very carefully and to look, in particular, at the tonsils. Tonsillar carcinoma in the dog is usually very aggressive with metastasis being present in 50-73% of cases at the time of diagnosis. It can be a very painful condition which is why some of these dogs found with enlarged lymph nodes, will need anaesthetising prior to examining their mouth. Once diagnosed with tonsillar carcinoma, treatment usually involves the multimodal approach of surgery, radiotherapy and chemotherapy. Unfortunately, treatment is not usually very successful with a 12-month survival rate in less than 10% of cases. A non-tonsillar SCC in the dog is much less likely to metastasise and for this reason treatment with surgical resection and radiotherapy is much more likely to be successful. David advises that chemotherapy for non-tonsillar SCC is of little value due to the non-metastatic nature of this tumour.

Melanoma is the most common oropharyngeal tumour in the dog and its position on the dog can be an important prognostic factor. For example, if found on haired skin of the dog, the melanoma is much more likely to be benign. However, if found at the mucocutaneous junction (except on the eyelids) the melanoma is much more likely to be malignant. Once a diagnosis has been confirmed through biopsy (a necessary step for diagnosing all oropharyngeal tumours), David advises always asking the lab to measure its mitotic index. Finding more than three mitotic cells in one high power field is usually a poor prognostic indicator with only 25-35% of cases surviving to one year. Treatment of melanoma usually involves surgically excising the mass with 2cm margins alongside removal of affected bone. Radiotherapy can also be performed and is particularly useful where surgery cannot be performed. Medical management may also be appropriate and involves the use of immunotherapy by administering a vaccine which stimulates an immune response to the melanoma. David advises in his experience, he only finds immunotherapy useful in patients whose tumour is locally controlled and where there is little evidence of metastatic spread. He believes it could help delay the onset of metastatic disease but is not convinced it has a huge beneficial effect.

As stated previously SCC is the most common oropharyngeal tumour found in the cat and is usually very aggressive with untreated cats often having a survival time of less than three months. Even with surgery and radiotherapy the mean survival time only increases to 10-12 months. SCC of the nasal planum and pinnae can be easier to manage with a pinnectomy controlling the disease for more than one and half years in some cases. Once again surgical resection of the nasal planum also offers good control but cases generally do better if surgery is performed prior to the SCC breaking through the basement membrane. Radiotherapy and photodynamic therapy can also be useful although, as stated before, the benefits are likely to be greater if treated prior to the tumour breaking through the basement membrane.

I have offered just a fraction of the information delivered within this webinar as David also discussed several other head and neck tumours found in cats and dogs including oral fibrosarcomas, epuli, thyroid tumours, parathyroid tumours, salivary gland tumours and ear canal tumours. David has, as always, delivered a practical and relevant webinar which can only be fully appreciated by logging into ‘The Webinar Vet’ and watching this rewarding hour long recording.