Vet360 Vet360 Vol 05 Issue 04 - Page 27

DENTISTRY Article reprinted with permission of DVM360 –August 14, 2018. DVM360 MAGAZINE is a copyrighted publication of Advanstar Communications inc. All rights reserved The ABCs of Veterinary Dentistry ‘O’ is for Oral Masses of the Malignant Kind The histopathology report from the oral biopsy came back as malignant— now what? Surgery? Radiation? Chemotherapy? Watchful waiting? By Jan Bellows, DVM, DAVDC, DABVP, FAVD If caught before metastasis, many malignant oral masses can be removed, leaving the patient with little to no facial deformity and a functional bite. Here’s an overview of the types of malignant oral masses you’re likely to encounter, as well as what to do about them. Common oral malignancies Here are the most commonly diagnosed malignant oral tumours in dogs and cats: Malignant melanoma. Malignant melanoma is a locally aggressive tumour that’s common in dogs and rare in cats and often metastasizes to the lungs (Figures 1A and 1B). Aggressive surgical excision, including partial mandibulectomy or maxillectomy, is the treatment of choice. Tumour sizes less than 2 cm carry a better prognosis than those greater than 4 cm. Figure 1A. A large oral mass involving left mandibular premolars and molar. (All images courtesy of Dr. Jan Bellows). However, radiation may have a role in effectively treating the primary tumor. In cases deemed nonresectable, or if an owner is unwilling to pursue surgery, radiation therapy has a high response rate (70% to 90%). Most protocols utilised are classified as hypofractionated in that they require only a few treatments, but each treatment has a high dose, or fraction. This involves three to four weekly fractions of 8 Gray or six weekly fractions of 6 Gray. Side effects, including oral mucositis, are generally mild and self-limiting with hypofractionated protocols. Similar to surgery, patients treated with radiation therapy may achieve local control but generally succumb to metastatic disease. Survival times of seven to nine months are common. Figure 1B. Cytology of the oral mass in Figure 1A consistent with melanoma. Issue 04 | AUGUST 2017 | 27