An oral tumor is an abnormal growth and unregulated replication of cells that occur within the mouth. A dog’s mouth, similar to our own, is made up of several different cell types; for example, there are epithelial (or skin) cells, bone cells, fibrous cells, and others all of which can become cancerous.
In a large number of cases, tumors are identified incidentally during annual dental exams. It is important to evaluate a patient’s whole mouth, including base of the tongue and tonsils during any dental procedure or other anesthetic event requiring intubation. Potential clinical signs owners may report include halitosis, bleeding from the mouth, hesitancy eating hard kibble, or the appearance of a visible mass.
Types of Oral Tumors in Dogs
1. Benign oral tumors
The word benign is defined as something that is not harmful. When directly related to tumors/cancer, benign is equated to not being malignant, or “dangerous/virulent.” While benign oral tumors are understandably less “scary” and often more treatable than malignant tumors, they should still be treated promptly. Even benign oral tumors often continue to grow, and unhampered growth can eventually lead to difficulty eating and chewing and destruction of local tissues. Prompt treatment equates to less aggressive surgery and a higher chance at surgical cure. We will explore some different types of benign oral tumors below.
Epulis
This is a benign oral tumor found in dogs. Epulis is a general term used to define a mass of any type arising from the gums. These tumors can occur at any age, but middle-aged and geriatric dogs are affected most often. Epulides are most common in dogs such as Pugs and Boxers. While considered benign epulides may invade underlying bone causing bone destruction and loose teeth.
2. Malignant Oral Tumors
Malignant Melanomas
Melanomas of the oral cavity originate from the mucosa or gingiva. They often have brown or black pigmentation, but can also be non-pigmented. Male dogs with heavily pigmented mucosa such as German Shepherds and Cocker Spaniels may be more predisposed. Malignant melanomas are characterized by rapid growth, local invasiveness, and early metastasis to regional lymph nodes and lungs. Over half of the cases will have bony invasion and lymph node metastasis at the time of presentation and approximately 15% will have detectable lung metastasis. This tumor carries the least favorable prognosis of all of the oral tumors.
Malignant Fibrosarcomas
Fibrosarcomas in dogs form in the oral cavity’s fibrous tissues, and are locally invasive, but only about one-third metastasize. Oral fibrosarcomas may appear as swollen areas anywhere inside the mouth. They frequently ulcerate, and may also become infected.
Squamous cell carcinoma
This malignant oral tumor is seen more often in cats than dogs. The mass may be found anywhere within the oral cavity, but occurs especially under the tongue. While this locally invasive cancer tends to avoid metastasis, it can also grow rapidly, which leads to a grave prognosis.
3. Cysts
Cysts are a subset of oral masses:
Dentigerous cysts are the most common cysts, which arise from the enamel-forming organ of an impacted tooth. They are most commonly found in mandibular first premolars of brachycephalic breeds. Their incidence in veterinary medicine has not been documented, but anecdotally they are found in approximately 50% of embedded teeth.
Radicular cysts are another type of cyst that develops from embryonic tissue remains, usually due to an inflammatory stimulus from the tooth.
As cysts grow, they cause bone loss by pressure. They can grow quite large in a short period of time, quickly resulting in weakened bone.
Management and Treatment of Oral Tumors in Dogs
Oral tumors in dogs can be difficult to manage. The first step is addressing pain and underlying infection. The preferred treatment may include a combination of surgery, radiation, and chemotherapy. If surgery is not an option, radiation and/or chemotherapy is recommended. With complete melanoma excision, immunotherapy may be helpful. Appetite stimulants or a feeding tube may be required to provide nutrition and medications. Dogs with an oral tumor need regular veterinary visits to monitor their status and prognosis. Discussing a personalized management plan with your veterinarian, and a veterinary oncologist, is important for the best outcome for your dog.
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