Benign and malignant oral masses are commonly encountered in the oral cavities of dogs and cats. Benign oral masses found
within the oral cavity do not metastasize, but they are often locally invasive. The behavior of malignant masses are type-
and, in some cases, site-dependent. This case describes a patient with such a mass and outlines the importance of early detection
and intervention of oral masses in veterinary patients.
A 9-year-old neutered male Standard Poodle was presented for evaluation of a 3-cm-diameter right mandibular mass extending
from the distal aspect of the canine to the mesial aspect of the third premolar (Photo 1). The dorsal and central portion
of the mass demonstrated a cavitation secondary to trauma from the opposing maxillary premolar. The owners reported recent
minor oral hemorrhage, seen as blood-tinged saliva. No discomfort was apparent on palpation of the mass, the surrounding bone
or the adjacent soft tissue.
Photo 1: A right mandibular acanthomatous ameloblastoma extending to the midline in the patient in this case. A surgical
approach to remove the mass requires a bilateral rostral mandibulectomy.
What should be done before biopsy?
Discussion of the options and intent of treatment with this patient's pet owners is essential. They should understand that
most oral masses can be successfully resected surgically. A discussion of potential common malignancies and their systemic
potential is also indicated. The worst prognosis comes with oral melanoma that is quick to metastasize. Squamous cell carcinoma
carries a poor prognosis if tonsillar involvement is present, but curative excision is possible in other oral locations if
the mass is detected prior to distant metastasis. Only 20 percent of fibrosarcomas metastasize, and excision plus or minus
radiation and chemotherapy are options. Pet owners must understand that masses of this size and extent often require partial
jaw removal. If they are unwilling to pursue therapy, biopsy is of no value to the patient.
In this case, the patient was anesthetized, and a deep wedge-shaped biopsy sample of the mass was obtained rostrally, avoiding
the traumatized portion. No sutures were placed, and bleeding was minimal. Histopathologic examination revealed acanthomatous
ameloblastoma. Formerly classified as acanthomatous epulis, acanthomatous ameloblastoma is a common benign but locally invasive tumor. Surgical resection by a board-certified veterinary
dentist or surgeon is the treatment of choice for this condition.
What considerations will be discussed with this client upon referral?
Had this been a malignancy, diagnostic tests to determine metastasis and staging would have predicated excision. In the case
of any locally aggressive oral mass, margin determination is ideally determined by computed tomography (CT). In this case,
CT was not readily available, and margin estimation was based on gross appearance because of the lack of radiographic changes.
In patients with acanthomatous ameloblastoma, a mandibulectomy or maxillectomy with a minimum of 1-cm margins is the treatment
of choice for definitive resolution.
Client education should also involve discussions regarding postoperative appearance and function. Pictures of past cases with
similar procedures provide pet parents a glimpse of postoperative cosmesis. Bilateral mandibulectomies involving excision
caudal to the mandibular symphysis result in elimination of direct anatomical communication between the two mandibles. Lateral
and ventral tongue deviation, drooling, and difficulty with food prehension and swallowing are expected and may be temporary
or permanent. Despite these alterations, patients generally retain an excellent quality of life and adapt to the resulting
anatomical alterations quickly.
Photo 2: This immediate postoperative image of the patient shows the extent of mandibular tissue excision. Safe margins into
normal tissue extend to the fourth premolar bilaterally.