Introduction
Squamous Cell Carcinoma (SCC) is a cancer that occurs in cats and dogs. The tumors can appear many places but are seen most commonly on and around the eyes, ears, nose, mouth, and areas with little hair.
Risk Factors/Detection/Staging
The primary cause of SCC is sunlight over-exposure, which is especially harmful to fair-haired cats. Age and exposure to cigarette smoke also increase the risk for SCC.(1) At first, SCC tumors look much like other common skin irritations, making them difficult to identify. Scabs, hair loss, irritated skin, loss of teeth with limited healing, and raised red bumps on the skin are all possible sign of SCC.(1) Crusty sores can appear and develop into deep ulcers that bleed when irritated. In later stages, the cancer may spread to the lymph nodes and lungs. Staging of the cancer may involve chest X-rays and testing lymph fluid.(2) In advanced cases, SCC tumors can cause tissue death and destroy bone structure, leading to pain, discomfort, and possibly death.
Treatment
Several treatment options exist for SCC and they may be combined to increase success. As with other cancers, the earlier SCC is detected, the more likely the treatment will be successful. Tumors in the lower jaw or upper ear can be surgically removed. Vets attempt to preserve as much healthy tissue as possible. For tumors in the lower jaw, vets can perform a surgical Mandibulectomy, in which they attempt to remove the cancerous area(s). The amount of the jaw tissue and bone removed depends on the tumor. Possible side effects include difficulty eating and grooming, drooling, and poor appetite.(1) Despite a cancer reoccurrence rate of 38% and post-operation complications, one survey revealed that over 80% of owners whose cats had surgery would choose this treatment again.(1)
Chemotherapy alone has not proven effective, but there is evidence that it may be effective when combined with other treatments. A combination of the chemotherapy agent mitoXANTRONE with external beam radiation therapy gave better results than either treatment option used alone.(3) If the tumor is in the mouth, radiation should be considered with caution as it can cause severe inflammation. Side effects may prevent normal eating and require the use of a feeding tube.
Cryotherapy or freeze-surgery involves insertion of a probe that freezes the tumor, killing the cancer cells. Cryotherapy is an option for tumors under 1 cm (about 0.4 inch) in diameter. The rate of reoccurrence is high for larger tumors.(4) Cryotherapy is a good option for tumors on the upper ear because the position allows for direct and aggressive treatment.
Photodynamic therapy (PT) is a newer treatment option for Squamous Cell Carcinoma, and is not available everywhere. This type of treatment involves putting a light-sensitive material in the tumor and exposing the tumor to a specific wavelength of light. This causes the light-sensitive chemical to become active and destroy the tumor cells.(5) It can be used repeatedly and with other treatment options.(6) The side effects include swelling, redness, sensitivity to light, and death of healthy tissue around the tumor site. A recent study followed 12 cats with SCC that were treated with PT. Researchers found that when used alone, PT resulted in shrinkage of shallow tumors of the nose and ear, but had little effect on deeper tumors. When used in combination with surgery, two cats exhibited a partial response to therapy, and one exhibited a complete response.(5)
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