The oral cavity is a very common area for cancer to occur. In dogs there are numerous benign growths, however in cats the incidence of non-malignant tumors is rare. It is impossible to determine whether a lesion is benign or malignant by simply looking at it. There are some signs such as bony invasion (or lack thereof) that can suggest malignant or benign tumors, but not consistently. In addition, malignant tumors behave very differently, and the treatment would then be different as well. For these reasons all oral lesions should be sampled and microscopically examined no matter how benign it appears.
There are many types of cancer that occur in the mouth, but some are much more common. In dogs, the most common benign tumor is an
epulid. This is a benign tumor of the periodontal ligament. There are numerous other benign growths as well, and they share in common that they are usually have well defined boarders, donít invade the bone or other tissues, donít metastasize (spread), and respond well to being surgically removed. Cats very rarely have benign growths in the mouth. The most common ones are eosinophillic granulomas or plaques, and periodontal inflammation. The eosinophillic growths respond well to corticosteroids, surgical removal, or diet change; the periodontal lesions to proper hygiene or possibly extraction of an offending tooth.
There are three common oral malignancies in dogs and cats. These are squamous cell carcinoma,
fibrosarcomas, and malignant melanomas. Squamous cell carcinomas are very locally aggressive, however tend to metastasize late if at all. They will very commonly affect the underlying bone. This is by far the most common tumor in cats, and the second most common in dogs. It is commonly found in older cats and dogs as an ulcerated red spot. The second most common tumor in dogs and cats is
fibrosarcoma. This behaves similarly to squamous cell, in that it is locally aggressive but does not tend to spread. It also appears as a red growth, which can be fibrous or ulcerated. This is often seen in older (>7.5 years) male large breed dogs. Melanosarcoma is the most common tumor in dogs, but very rare in cats. This tumor is locally invasive, but also metastasizes early in the disease course. Usually by the time it is diagnosed, it has already spread. It is most commonly seen in older dogs that have dark pigmented oral mucosa. It can either be dark or light gray. Another tumor seen infrequently in dogs is an acanthomatous
ameleoblastoma. This tumor is locally aggressive, but does not tend to spread. Unfortunately there is usually a significant amount of local destruction by the time it is diagnosed, however this tumor responds well to aggressive surgical excision.
There are numerous techniques for treating oral tumors in animals. The mainstay of therapy is surgical excision. If this is possible, it is the most effective means of achieving a cure. The major problem with surgery in malignant tumor cases is the size of the piece of tissue that needs to be removed. Because these tumors are invasive, they send out fingers of tumor cells into the normal tissue. This cannot be seen visually or radiographically, and may not even be diagnosed under the microscope. To ensure complete removal of the tumor, the surgeon will remove 2 cm of normal appearing tissues all around the visible tumor. This is a large surgery! However radiation therapy, cryosurgery (freezing), and chemotherapy have all been used alone or in combination with surgery.
Large oral mass in the mandible
of a dog
Postoperative healing of a caudal maxillectomy for oral neoplasia in a dog
Squamous cell carcinoma in a
5 year old golden retriever
Radiography shows considerable dissolution of bone around the incisor.
Excision via rostral maxillectomy was curative.