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Oral Cancers and Lesions in Dogs and Cats


Types, Descriptions, Symptoms, and Treatment

Oral tumors account for approximately 6% of all canine cancers and about 3% of all cancers found in cats according to veterinary statistics. It is the 4th most common cancer of male dogs and is 2.6 times more likely to develop in dogs than in cats. On the whole, males of both species are more likely to develop oral cancers than are females.

The mouth is a common site for both benign and malignant cancers. The most usual benign tumor in both dogs and cats is called epulides, normally seen as round, hard masses arising from the gingival tissue. Malignant tumors including oral melanoma, fibrosarcoma, squamous cell carcinoma, and oral osteosarcoma and can be found in both dogs and cats. We have described the most common oral tumors and lesions below, including what to look for, information on what ages and breeds are most predisposed to particular cancers, and what veterinary diagnosis and treatment is available to both dog and cat owners.

Types of Oral Cancers

Oral Melanoma – Melanomas are aggressive cancers of the melanocyte cells – those octopus-shaped, pigment-producing body cells that line the bottom layer of the epidermis, the first layer of skin. Most commonly seen on your pet’s gums and the areas close to the tongue, melanomas may also involve the palate of the mouth and the dorsal, or upper, surface of the tongue. Oral melanomas are considered highly malignant, with 30- to 40% of the tumors quickly metastasizing to the animal’s lymph nodes and lungs. Unfortunately, the average lifespan of an animal following malignant melanoma diagnosis is five to eight months. The tumors appear as fleshy masses and can be pigmented or non-pigmented. The most common oral malignancy in dogs, melanomas most frequently occur in older dogs with darkly pigmented areas of the mouth, tongue, and gums. Oral melanomas are relatively rare in cats, but when found, typically develop in older cats and are, unfortunately, usually aggressively malignant.

Fibrosarcoma – Fibrosarcomas are cancerous tumors that originate in the fibrous, connective tissues of your cat or dog’s bones, usually the periosteum covering of the long bones. Oral fibrosarcomas most commonly occur on the maxilla (the upper jaw), but have been known to grow on the mandible (the lower jaw) of companion animals. The tumors can be seen as an extended, overgrown lesion on the animal’s jaw. Felines afflicted with oral fibrosarcomas are, on average, 7-½ years old with predominantly male cats developing this disease. The average age of presentation is the same for dogs, 7-½ years, with larger male dogs, particularly Golden Retrievers, prone to the tumors.

Squamous Cell Carcinoma – Squamous cell carcinoma is a cancer of a kind of skin cell, the squamous cell. These large, flat cells make up the outer layers of your pet’s skin; they can also occur in the mucous membranes of your pet’s lips, mouth, esophagus, and nose. Oral squamous cell carcinoma can be most commonly seen as a rounded, suppurating mass or lump on the gums, just above the canine teeth. It has also been shown to occur on the tongue and in the back of the throat. The closer the cancer is located to the lymph nodes of the throat, the more likely it is to metastasize to other parts of the body.

This type of cancer is most often found in dogs between 6 and 10 years of age, with Keeshonds, Basset Hounds, Collies, and Standard Schnauzers showing a predisposition for the disease. Older cats, as well, are more likely to develop this disease, with it showing up predominantly on the lips and nasal planum (the front of the nose).

Oral Osteosarcoma – Oral osteosarcoma is a malignant cancer of the bone, and, when found in dogs and cats can affect the bones of the skull, including the mandible and the maxilla (the lower and upper jaws). Where the cancer is located is directly related to the animal’s prognosis. Veterinary studies report that dogs and cats with osteosarcoma in the lower jaw have a better prognosis than those with cancer in the upper jaw, living approximately 9 months longer, with 1-year survival rates ranging from 35- to 71%. In order to best control the local tumor, complete surgical removal must be achieved. Those animals with both upper and lower jaw involvement survived the longest, on an average of 4 years versus 6 months, when a complete removal of the tumor and surrounding tissue was accomplished through surgery. The tumors rarely metastasize to other organs.

Canine breeds predisposed to develop oral osteosarcoma include Rottweilers, Saint Bernards, Great Danes, Golden Retrievers, Irish Setters, Dobermans, and Labradors. While uncommon in smaller breeds, your Poodle or Pug can indeed get this neoplasm. The disease typically develops in dogs a year old and then again at 7-½ years of age. This cancer in younger dogs has been found to be more aggressive than that found in older patients. Feline osteosarcoma typically occurs in aging cats over the age of 10 years and is known to be very aggressive.

Benign Oral 
Epulides – Epulides are firm benign masses that form on your pet’s gingival, or gum, tissues. More common in dogs than cats, epulides are generally single, noninvasive masses that can grow to be quite large and troublesome, although multiple masses may be found in some animals. One type of epulides, called ossifying epulis, develops hard, stone-like centers that can be painful when the animal attempts to chew. They arise from the periodontal ligament (the ligament that attaches the tooth to the bone) of the adjacent tooth, and only complete excision of the tumor, surrounding tissue, the ligament, and, often, the tooth will affect a cure.

These tumors may be seen in dogs of any age but generally are found in those over 6 years old; they appear as marble-like, smooth, round masses. Epulides are the fourth most common oral tumor in dogs and occur most often in the brachycephalic (short-nosed) breeds. Boxers tend to have a greater incidence of epulides than other breeds of dog. These tumors are rare in cats, but occur most often in the short-nosed breeds, like their canine counterparts. Persians, Himalayans, and Scottish Folds are more commonly affected.

Symptoms

The symptoms of oral tumors are the same for both dogs and cats. They include:

  • Growths in the mouths that can be seen by the naked eye
  • Difficulty chewing, also called dysphagia
  • Unexplained weight loss
  • Excessive drooling
  • Bad breath (halitosis)
  • Loose teeth
  • Blood coming from the mouth, or bloody saliva
  • Swollen or enlarged areas on the face usually under the eyes
  • Enlarged lymph nodes just under the jawline

If you notice any of these symptoms in your cat or dog, please make an appointment to see your veterinarian as soon as possible.

Diagnosis

To provide a definitive diagnosis, your veterinarian will need to take a complete physical examination of your pet, palpating lymph nodes and the facial region for any inflammation, and looking for oral lesions on the lips, nose, and outer surfaces of the gums. The doctor will closely check the inside of your pet’s mouth to see if there is any noticeable growth. A complete blood profile is typically requested, including a complete blood count, chemical profile, and a urinalysis. Radiographs may be taken of your pet’s head and chest to show the extent of the mass, and to determine if any cancerous tumors have spread to other organs in the body.

Additionally, veterinarians usually want to take a fluid sample from the lymph nodes to look for cancerous cells and will perform a biopsy of any oral mass to determine exactly what kind of tumor is present. When taking these last two samples, your pet may need to be sedated and/or placed under general anesthesia.

Treatment

The veterinary treatment of oral cancers in your dog or cat typically depends on what stage of the disease is present and whether the cancer has metastasized to other areas of the body. In most cases, doctors recommend chemotherapy after making a definitive diagnosis as to what kind of neoplasia (cancer) is present. Radiation therapy may also be performed in conjunction with the chemotherapy to reduce the size of the tumor and to assist in the effectiveness of the chemo. If the cancer has not spread, veterinarians commonly suggest surgically excising the tumor and any surrounding tissue that might be carrying cancerous cells.

If the cancer has spread, chemotherapy and radiation will be performed first to try and isolate the cancer. The prognosis is usually very good when surgery follows this treatment protocol.