Oral Tumors in Cats - An Overview

By Malcolm Weir, DVM, MSc, MPH; Jan Bellows, DVM, Dipl. AVDC, ABVP; Christopher Pinard, DVM

What is an oral tumor?

An oral tumor is an abnormal growth of cells. A cat’s mouth, similar to our own, is made up of several different cell types; all of which can become cancerous (e.g., skin cells, bone cells, fibrous cells). Some tumors may grow slowly and do not typically spread, called benign, while others will act aggressively called malignant. In cats, more than 90% of oral tumors are, unfortunately, malignant.

What causes this cancer?

The reason why a particular cat may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary.

Exposure to cigarette smoke, feeding high levels of canned food, and the use of flea collars are possible contributing factor for the development of squamous cell carcinomas in cats.

"Very few tumors and cancers have a single known cause."

What are the signs of oral tumors?

Oral tumors come in many forms and your cat's signs will depend on location of the tumor, tumor type, and tumor size. Tumors may appear as swellings on the gums around the teeth, on the hard palate, or on the soft palate. . They frequently ulcerate (break open) and bleed. They may also become infected.

Tumors may look small but often extend deeper into the tissues than expected, invading the underlying bone. Alternately, the bone may be affected first causing significant tissue swelling and oral swelling.

Oral pain is usually apparent, especially in cats with tumors that have penetrated the underlying bone. Signs may include bad breath (halitosis), drooling, panting, movement or loss of teeth, lack of appetite or difficulty eating, reluctance to be touched on the head, facial swelling, and swelling of the lymph nodes.

How is this cancer diagnosed?

An accurate diagnosis of oral tumors requires microscopic examination of tumor tissue. Fine needle aspiration (FNA) involves taking a small needle with a syringe and suctioning a sample of cells directly from the tumor and placing them on a microscope slide. Your veterinarian or a veterinary pathologist then examines the slide under a microscope. In some cases, a biopsy is necessary.

A biopsy is a surgical excision of a piece of the tumor. Pieces of the tumor are then examined under the microscope. This is called histopathology. Histopathology is not only helpful to make a diagnosis but can indicate how the tumor is likely to behave (probability of local recurrence or spread to other areas).

How does oral cancer typically progress?

If the tumor is benign it may enlarge locally. Malignant tumors are commonly locally aggressive, meaning it will invade the closely associated tissues and structures (tooth roots, bone, and other soft tissues). In cats, the reported metastatic rate (spread rate) is suspected to be low, however it is possible. The biggest concern is local disease, meaning local disease that invades locally to the tooth roots and bone.

What are the treatments for oral tumors?

Surgical removal is the standard treatment for all oral tumors. Magnetic resonance imaging (MRI) scans of the head/neck may be performed before surgery to determine the extent of disease, as well as for surgical planning. When mandibular lymph nodes are affected, they are typically removed at the same time as tumor removal.

"Surgical removal is the standard treatment for all oral tumors."

If the tumor has invaded bone, its removal may be difficult, and it may be necessary to remove a portion of your cat’s jaw. Although this type of surgery sounds daunting, many of these tumors are painful and surgical removal provides relief. After surgery, the tissues are sent for to a pathologist to predict, the probability of local recurrence or spread to other areas. If the entire tumor is submitted, the pathologist may be able to assess if the tumor was completely removed or if additional therapies (a second surgery, radiation, or chemotherapy) are necessary.

In some cases, surgery may not be possible or warranted. Radiation therapy can also be considered as a primary treatment option if surgery is not possible; however, success rates are low. Immunotherapy (Oncept®) for oral melanoma in dogs is sometimes used for the same condition in cats, although studies to determine it’s usefulness are lacking.  If a malignant tumor has not been completely removed, a second surgery may be required or follow-up treatment with radiation therapy.

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