Non-Odontogenic Tumours

Squamous Cell Carcinoma (SCC)

In a survey of dogs with oropharyngeal tumors, SCC was the second most frequently diagnosed oral tumor (24.5 %), and sites of involvement included gingiva, tonsil, oral mucosa, lip and palate. In two surveys of oropharyngeal tumors in cats the most frequently diagnosed tumor was SCC, representing 61–64% of the oral tumors.

The mean age of dogs with gingival SCC was 8.4 years; no sex or breed predilection was noted. The tumors were described as typically reddened, friable and vascular. The clinical history frequently included tooth extraction with subsequent tumor growth at the extraction site.

Mandibular/Maxillary Squamous Cell Carcinoma in Dogs and Cats

Surgical resection typically requires a partial mandibulectomy or maxillectomy. Determination of the extent of the disease radiographically or based on computed tomography imaging aids in surgical planning. Long-term control is possible with aggressive local resection of oral SCC. There have also been a number of reports that document the efficacy of radiation therapy in the treatment of canine oral SCC. Cats with oral SCC are typically diagnosed late and the response to therapy is poor. It is not uncommon for cats to present with a palpable or visible enlargement of the mandible or maxilla and a history of recent dental treatment.

Lingual/Sublingual Squamous Cell Carcinoma in Cats

In one report, 61.2% of cats with oral tumors had SCC and most occurred sublingually. Careful evaluation of the oral cavity with examination under the tongue as well as palpation of the tongue will provide information on location and extent of disease. Tumor extension into the musculature of the tongue is firm on palpation and will cause rigidity and decreased mobility of the tongue

Tonsillar SCC

Tonsillar SCC has a higher rate of metastasis than gingival tumors, presumably due to the fact that tonsils are richly supplied with efferent lymphatics that drain to the ipsilateral as well as contralateral mandibular and retropharyngeal lymph nodes. Tonsillar SCC is very uncommon in cats.

Papillary Squamous Cell Carcinoma of Young Dogs

There is a distinct entity of papillary SCC that occurs in young dogs that may be associated with papillomavirus. The tumors appear locally aggressive with underlying bone lysis. The dogs respond well to a combination of surgery and orthovoltage radiotherapy. There have been no reports of metastasis in dogs with papillary SCC.

Malignant Melanoma (MM)

Malignant melanoma is the most common malignant oral tumor in dogs. Males are predisposed, with a male to female ratio of 3 : 1 to 6 : 1, and mean age of 10.5–12 years. The majority of MM involve the gingiva. Other sites of involvement include the labial mucosa, palate, buccal mucosa and tongue. Melanomas are uncommon in cats, with ocular and cutaneous sites more common than the oral cavity. Melanomas of the lip that arise from mucous membranes typically have a better prognosis than gingival tumors but are more aggressive than tumors arising from haired skin. Melanomas are firm, greyish or brownish black, rapidly enlarge, develop ulceration, hemorrhage and metastasis within weeks or months.

Fibrosarcoma (FS)

The third most common tumor in dogs was fibrosarcoma representing 17.7% of oral tumors. In tumors in cats, FS represented the second most common oral tumor representing 12.9% and 22.0% of the oral tumors in two surveys. Surgery alone for oral FS results in a relatively high local recurrence rate. A histologically low-grade yet biologically high-grade FS of the mandible and maxilla is a distinct histopathologic entity that has been identified in dogs. The histopathologic appearance is compatible with benign fibrous connective tissue but the biologic behavior indicates otherwise, with 72.7% of dogs evaluated found to have underlying bone lysis. Additionally, 12.0% ultimately developed pulmonary metastasis and 20.0% regional lymph node metastasis. The most common breed affected appears to be Golden Retrievers.

Other Non-Odontogenic Oral Tumours

Osteosarcoma

Osteosarcomas occur more commonly in the appendicular than axial skeleton.

Extramedullary Plasmacytoma

Extramedullary plasmacytomas arise outside of bone, are typically mucocutaneous in location and occur most commonly in the mouth, on the feet or trunk and in the ears. When they occur in the oral cavity the locations reported include the gingiva, tongue, hard palate and oropharnyx.

Oral Lymphoma

The sites of involvement included tonsils and cervical lymph nodes, membrana nictitans, soft palate, gingiva, buccal mucosa, pharynx, tongue and epiglottis. Epitheliotropic lymphoma in dogs can involve the gingiva and/or lips at the mucocutaneous junction. Radiation therapy has been used in the management of local disease in the oral cavity in addition to systemic chemotherapy, although detailed information is lacking on response to therapy.

Oral Papillomas

Oral papillomas can be solitary but are often multiple cauliflower-like growths that may have frond-like projections. This tumor occurs most commonly in young dogs. Canine oral papillomatosis virus is contagious from one dog to another. Treatment in clinical cases is usually not necessary as the lesions will typically regress spontaneously. Excisional surgery, laser surgery or cryosurgery may be indicated in dogs that have multiple lesions that cause difficulty eating.

Salivary Gland Tumours

Adenomas and carcinomas.