Squamous Cell Carcinoma
Squamous cell carcinomas are the malignant equivalent of the papilloma and may arise anywhere within the oropharynx. They are common in the cat, horse and cow. They are most likely to develop in non-pigmented areas of the skin.
The level of malignancy is often related to the location of the neoplasm. Those arising over the tonsil (squamous carcinoma of the tonsil or tonsillar carcinoma) are very malignant, invading adjacent tissues and metastasising early. Squamous carcinomas of the tongue (especially in cats) can also behave in a very malignant fashion. Those at more rostral sites, e.g. on the incisor gingivae, are less likely to metastasise early although they may be locally aggressive.
Cattle
As mentioned, squamous cell carcinomas are most likely to develop on non-pigmented areas of skin such as the eyelids. There is thought to be an association between the ingestion of bracken fern carcinogens and the malignant transformation of papillomas to squamous cell carcinomas in cattle.
- Squamous cell carcinomas of the oropharynx in cattle are commonly seen as part of an upper alimentary tract carcinoma complex.
Cat
- Squamous cell carcinomas of the oesophagus are occasionally seen in other species, notably in the cat, where the tumour tends to infiltrate around the oesophageal wall resulting in a “ring carcinoma”.
- The affected cat has progressive difficulty in eating and swallowing.
- Forms part of Upper Alimentary Tract Carcinoma Complex
Horse
- The most common gastric tumour in the horse.
- Affects the pars oesophagea.
- Take the form of a large cauliflower-like mass.
- Metastasises, and spreads and transcoelomically.
Nasal Cavity
- In cats they arise mainly from nasal vestibule
- In horses they originate mainly from maxillary sinus
- Most common nasal tumour
- Serosanquineous or mucopurulent, odourous nasal discharge
- Tissue necrosis
- May cause airway obstruction or facial distortion