Managing canine oral tumors

Photo: GaiBru/Adobe Stock

Canine oral cavity masses are commonly identified, often as an incidental finding during dental prophylaxis or because of clinical signs identified by owners. Clinical signs can include foul odor from the mouth, abnormal or altered prehension or eating patterns, hypersalivation, blood in the water or food bowls, or a grossly visible mass. These masses can range from inflammatory lesions to hyperplastic lesions to benign or malignant neoplastic diseases. As such, prognosis and treatment recommendations vary based on the type of lesion identified.

Several important steps should be taken and/or considered after the identification of an oral cavity lesion:

• Perform a thorough oral examination. This is best performed with the canine under heavy sedation and/or anesthesia.
• Document the location of the mass in the medical record as per the modified Triadan system, including details on the location of the mass relative to the teeth (buccal or lingual/palatal) or other pertinent anatomic structures.
• Consider taking digital photographs. Because of the complexity of oral cavity masses, digital photographs of the mass are recommended as part of the medical record. This may be of particular importance if the mass requires a more extensive surgical excision following definitive diagnosis.
• Perform diagnostic tests aimed at identifying the origin of the oral cavity mass to guide treatment recommendations and prognostic discussions

Diagnostic investigation of oral cavity lesions typically begins with direct sampling of the lesion to determine a benign or malignant behavior. Cytological evaluation via fine-needle aspiration or impression smears can be a minimally invasive option to achieve a diagnosis and has a high level of agreement with histologic diagnoses.¹ However, when aiming for a potential definitive treatment, clinicians may prefer to perform incisional or excisional biopsies. The previously mentioned documentation recommendations are of particular importance if excisional biopsies are being considered. If a definitive diagnosis of a malignant tumor or a benign but locally invasive tumor is made, further treatment may be required. Because there may be no gross disease visible to guide additional diagnostics and treatments, the previous documentation will be an important guide to ensure the correct location is being evaluated and treated.

The overall incidence of canine oral tumors is higher than previously reported2 and may be attributed to improved medical care for pets and to pet insurance, resulting in more animals receiving routine medical care than in the past. Canine oral tumors make up approximately 6% to 7% of all reported canine neoplasms³ and tend to be malignant more often than benign.² The most common oral tumors in dogs are melanoma, squamous cell carcinoma (SCC), fibrosarcoma, and acanthomatous ameloblastoma, and the most common site for oral tumors in dogs is the gingiva,⁴ with some tumors having additional site predilections or locations.

The most common canine oral tumor types and their site/location predilections are as follows³:

• Melanoma—gingiva, buccal or lingual mucosa
• SCC—rostral mandible
• Fibrosarcoma—maxillary gingiva, hard palate
• Acanthomatous ameloblastoma—rostral mandible

Although melanoma, SCC, and fibrosarcoma exhibit malignant behavior, acanthomatous ameloblastomas have a benign but locally invasive behavior pattern.³ Metastatic potential is highest for melanoma cases, with a lower rate of metastasis for SCC and fibrosarcoma and no reported metastases for acanthomatous ameloblastoma cases.3 Despite the lack of metastatic potential for acanthomatous ameloblastomas, their local invasion into the surrounding bone results in diagnostic investigation and surgical treatments similar to those for malignant tumors.³

After a definitive diagnosis of any of these tumors, additional diagnostic investigations are recommended. Typically, this includes advanced imaging of the skull to assess the local extent of disease to aid in surgical planning and investigations aimed to rule out regional and distant metastases, such as local lymph node aspiration and thoracic imaging. Surgical treatment for these most common tumors of the mandible and maxilla entails a regional mandibulectomy or maxillectomy. Despite the gross soft tissue nature of these masses, excision of the underlying bone is required due to the tissues of origin of these tumors, invasion of local bone, and the increased risk for local recurrence when soft tissues only are excised.³

Despite a relatively invasive surgical treatment process, many dogs recover well from surgery and return to normal oral functions, including prehension, mastication, and drinking.⁵ Partial mandibulectomies and maxillectomies can have minimal impact on cosmesis, depending on the site and extent of disease, and owners have reported both formally⁵ and anecdotally that their pet’s quality of life is good postoperatively. Because the invasiveness of definitive treatment for oral tumors can often affect owners’ decision-making, veterinarians are encouraged to highlight the good quality of life, minimal cosmetic alteration, and reasonable recovery times postoperatively during these discussions.

Katie Hoddinott, DVM, DVSc, BSc, DACVS-SA, is a native of Nova Scotia, Canada. She graduated with her DVM from the Atlantic Veterinary College, University of Prince Edward Island, in 2012. She then completed 2 internships and a surgery residency at the Ontario Veterinary College, University of Guelph. She became a diplomat of the American College of Veterinary Surgeons – Small Animal in 2019. Hoddinott is currently working at the Atlantic Veterinary College as an assistant professor in small animal surgery, where she enjoys teaching undergraduate veterinary students, interns, and residents. Her professional interests lie mainly in surgical oncology and minimally invasive soft tissue surgery. Her current research focuses include advances in clinical teaching for surgery residents and surgical site infections.

REFERENCES

1. Bonfanti U, Bertazzolo W, Gracis M, et al. Diagnostic value of cytological analysis of tumours and tumour-like lesions of the oral cavity in dogs and cats: a prospective study on 114 cases. Vet J. 2015;205(2):322-327. doi:10.1016/j.tvjl.2014.10.022
2. Cray M, Selmic LE, Ruple A. Demographics of dogs and cats with oral tumors presenting to teaching hospitals: 1996-2017. J Vet Sci. 2020;21(5):e70. doi:10.4142/jvs.2020.21.e70
3. Liptak JM, Withrow S. Oral tumors. In: Kudnig ST, Séguin B, eds. Veterinary Surgical Oncology. Wiley-Blackwell; 2012:119-178.
4. Satthathum C, Srisampane S, Jariyarangsrirattana P, Anusorn P, Sattasathuchana P, Thengchaisri N. Characteristics of canine oral tumors: insights into prevalence, types, and lesion distribution. J Adv Vet Anim Res. 2023;10(3):554-562. doi:10.5455/javar.2023.j709
5. Bull I, Ziener ML, Storli SH, Arendt ML. Quality of life after partial mandibulectomy or maxillectomy in 45 dogs with oral tumors. J Vet Dent. 2023;40(4):329-337. doi:10.1177/08987564231164483