Oral Tumors in Cats - Fibrosarcomas

By Tammy Hunter, DVM; Jan Bellows, DVM, Dipl. AVDC, ABVP; Christopher Pinard, DVM

What is an oral fibrosarcoma?

Fibrosarcomas are the second most common oral tumor in cats. These tumors arise from the fibrous and connective tissues of the oral cavity. These tumors are very invasive locally (meaning they invade the adjacent tissues) which can make management difficult.

What causes this cancer?

The reason why a particular cat may develop this, or any 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. No known environmental, genetic, or hereditary cause has been determined for oral fibrosarcomas in cats.

What are the signs that my cat as this type of tumor?

Lesions may appear as thickened areas inside the mouth or may be more nodular or cauliflower-like in appearance. The lesions frequently ulcerate (break open), bleed, and may become infected. These tumors may look small but may extend deeper into the tissues than expected, invading the underlying bone.

The signs your cat may exhibit are dependent on the location, size, and how much the tumor has spread. Oral pain is usually apparent, especially in cats with tumors that have penetrated the underlying bone. Your cat may exhibit bad breath (halitosis), excessive drooling, excessive panting, discomfort while eating or dropping food, lack of appetite, displacement or loss of teeth, reluctance to be touched on the head, facial swelling, and painful swelling of the local lymph nodes. If the tumor has spread to the nasal cavity, your cat may have difficulty breathing from the affected nostril and may have discharge from the nose.

How is this cancer diagnosed?

Fine needle aspiration (FNA) may be performed, but usually cannot accurately diagnose these types of tumors. 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. A veterinary pathologist then examines the slide under a microscope.

For a definitive diagnosis, and prediction of how the tumor may behave (grow or spread), a biopsy is required. A biopsy is a surgical excision of a piece of the tumor. Your veterinarian may remove a small piece of the tumor, or the entire tumor for diagnosis. Pieces of the tumor are then examined under the microscope by a pathologist. 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 this cancer typically progress?

These tumors tend to behave aggressively by invading the local and surrounding tissues, with metastasis (spread to other organs) reported as rare.

Some fibrosarcomas will look non-aggressive (low grade) when observed under the microscope; however, they will behave aggressively. Therefore, aggressive therapy with any diagnosis of a fibrosarcoma, regardless of suggested behavior, is recommended.

"Aggressive therapy with any diagnosis of a fibrosarcoma, regardless of suggested behavior, is recommended."

Full staging (searching for potential spread to other locations in the body) is highly recommended for malignant tumors, as they tend to spread. This may include bloodwork, urinalysis, X-rays of the lungs, and possibly an abdominal ultrasound. If lymph nodes, particularly those located under the chin (submandibular lymph nodes), are enlarged or feel abnormal, further sampling by FNA may be pursued to determine if spread is present.

What are the treatments for this type of tumor?

Surgical removal is the standard method for treating fibrosarcomas. A CT scan or MRI of the head and/or neck region are generally recommended prior to surgery to determine the extent of disease and for surgical planning.  If lymph nodes under the chin (mandibular lymph nodes) are affected, they will typically be removed during surgery. They may be removed as a preventive measure to ensure there is no spread locally.

Depending on how invasive the tumor is, surgery may involve removing a portion of the top or lower portion of your cat’s jaw. Although this type of surgery sounds daunting for you and your cat, many of these tumors are painful and surgical removal provides relief.

After surgery, the tissues are sent for histopathology to predict, as best as possible, the probability of local recurrence or metastasis (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.

Is there anything else I should know?

Even with surgery, recurrence (or regrowth) is possible. These tumors do not respond well to chemotherapy or radiation therapy, however radiation therapy used in conjunction with surgery may be considered to help slow the progression of the disease. Prior to surgery and after treatment, cats may benefit from soft or canned foods, alleviating discomfort encountered with standard kibble. Pain medication and often antibiotics are also required to improve the cat’s quality of life.

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