Published on November 14, 2016
Tumors in the mouth are common in dogs. They can grow from the gum, cheek, palate, tonsil or periodontal tissue.
Unless they arise in the front of the mouth or are easy to see when a pet yawns, oral masses may not be noticed by an owner unless they cause drooling, gagging or trouble eating. One of the most common symptoms — bad breath — is often attributed to periodontal disease and ignored in the short term. Sometimes, bleeding from the mouth or external swelling of the jaw or face is noticed. Many cause no obvious symptoms at first.
Because these masses may be malignant, early detection, removal and biopsy allows the best outcome for your pet.
Malignant tumors found in the mouth
The most common cancerous tumor seen in the mouths of dogs is the malignant melanoma. It is usually darkly pigmented and grows very rapidly. Since it is quick to metastasize, the patient has a poor long-term prognosis — even with aggressive treatment.
The most effective control involves radical oral surgery, removal of associated lymph nodes, local radiation and systemic chemotherapy. A malignant melanoma vaccine is available through veterinary oncologists. This may extend remission, especially if the tumor has also been aggressively treated as outlined above.
It has a slight breed predisposition for poodles, dachshunds, golden retrievers, Scottish terriers, Rottweillers and black cocker spaniels, but can occur in any dog.
These tumors are the second most common oral malignancy of dogs. They arise from tissue below the gum and may appear as a smooth, rounded mass along the gumline. They are more common in older large breed dogs, and frequently arise near the upper fourth pre-molar (the largest upper cheek tooth).
Fibrosarcomas generally do not metastasize, but are very destructive to surrounding bone and tissue, causing pain. Surgical removal with tumor-free margins is very difficult as this cancer spreads tentacle-like into surrounding tissue.
Very early detection and extensive surgery has the best prognosis. Palliative radiation therapy and/or treatment with oral pain medication can be a short-term option if the tumor is too large for complete removal.
Squamous cell carcinoma (SCC)
This is another cancerous oral tumor of large breed, older dogs. These masses are more likely to be ulcerated and accompanied by oral odor, drooling and bleeding than melanomas or fibrosarcomas. Biopsy of a non-healing tooth extraction site will frequently reveal the early presence of a SCC.
This cancer can metastasize as well as locally invade bone and tissue. Surgery plus radiation and chemotherapy can provide limited control, but the prognosis is generally poor. Tumors occurring further back in the mouth are less responsive to treatment than those occuring near the front.
This cancer of the bone most commonly occurs in the leg bones of dogs, but it can occasionally occur in the upper or lower jaw. As in the legs, this tumor is highly destructive to bone and painful. Since amputation of the jaw is more complicated than limb amputation, this is another difficult oral cancer to treat.
Benign tumors in dogs
The most common oral tumor in dogs is the epulis. It arises from the periodontal ligament and occurs more commonly in middle-aged and older dogs. Short-nosed breeds like boxers and bulldogs may be more susceptible.
For most, surgical removal along with removal of the associated tooth is curative. Without removal of the tooth, they will recur.
The most aggressive type (acanthomatous) will invade bone and can be painful, but does not metastasize (spread to distant parts of the body). With a large acanthomatous epulis, it may be necessary to remove a large portion of the jaw. This is a major surgical procedure, but surprisingly well-tolerated by our patients.
Warts are occasionally seen in the mouths of dogs. These are caused by an infectious canine papilloma virus, so previously unexposed young dogs and immunosuppressed dogs, like those undergoing chemotherapy for cancer, are most susceptible.
This virus is highly contagious and spread easily by communal dog bowls and contact between young, social dogs at dog parks or doggy daycare. Once exposed, most dogs become immune and the papillomas generally regress without treatment within about eight weeks. Occasionally, dogs with very large numbers of warts will be uncomfortable and surgical removal may be necessary.
How early detection helps
Since optimal treatment of most oral tumors involves surgery, finding the mass when it is still small is important. Clinical signs may be absent until a tumor is quite large, so early detection is often made during a pet’s routine dental cleaning procedure.
Placing dogs under general anesthesia is the only way to do a thorough oral exam, and if an abnormality is found, X-rays and biopsy can be performed to get a diagnosis.
In many cases, biopsy results are benign and little-to-no treatment may be necessary. If the mass is malignant, early detection will give you the best chance for appropriate and reasonable treatment. The goal is to preserve your pet’s quality of life, keeping them pain-free and happy for as long as possible.