Solar-Induced Squamous Cell Carcinoma in Cats

Squamous cell carcinoma is a cancerous disease that mostcommonly involves skin. Fair-skinned people tend to bepredisposed to this type of cancer after chronic, excessiveexposure to sunlight. Likewise, white or light-colored cats arealso susceptible to squamous cell carcinoma. Solar-inducedsquamous cell carcinoma usually occurs in areas with little haircoverage that are chronically exposed to sunlight. The mostcommon area affected in cats is the ear tip.This disease occurs in older cats and may first become apparentin summer, when sunlight exposure is greatest. The first symptomof this disease that you will notice is reddening of the eartip. Other early signs of this disease include mild hair lossand flaking of skin on the ear tip. Usually the first impressionis that your cat has psoriasis, in which the skin seems scalyand inflamed. If caught early, these clinical signs may beindicative of the precancerous form of the disease known asactinic dermatitis. A small skin biopsy is required to differentiate precancerousactinic dermatitis from squamous cell carcinoma. It is best toperform the biopsy procedure early because the clinical lesionsof squamous cell carcinoma are subtle and similar to this formof dermatitis. One or both ears may be affected. If only one earis diseased, the other should be monitored closely because itmay also acquire the disease in the future.Early, effective treatment of precancerous lesions may preventthe onset of squamous cell carcinoma. Treatment for actinicdermatitis includes sun restriction, especially during times ofpeak solar intensity; water-resistant sunscreens with sunprotection factor (SPF) 15 or greater applied to the ear tipstwice daily; topical steroid application; and possibly oralsteroid or anti-inflammatory therapy. The drug etretinate may also be used to alleviate symptoms. Theeffect of etretinate is to decrease inflammation and skinflaking while normalizing skin cell metabolism. Medical therapyis not effective for lesions that advance to squamous cellcarcinoma, underlining the importance of early diagnosis forsuspicious lesions. Surgical removal of squamous cell carcinomaof the ear tip (partial pinnectomy) is most effective whenperformed as soon after diagnosis as possible. Earlyintervention decreases the amount of the ear that must beremoved, because the lesion is smaller. Early surgical removal also decreases the incidence of spread ofthe cancer to the lymph nodes near the ear. There are differentsurgical methods that are effective in removing the cancer. Withcryosurgery, like frostbite, the ear tip is frozen. The frozentissue dies and is removed. Although this method may beeffective, it is sometimes difficult to control the precise areaof tissue freezing. Freezing an inadequate area may lead torecurrence of the cancer, and excessive freezing may result inan unsightly appearance and be associated with excessive scarand deformation of the remaining ear. Laser surgery is available in veterinary medicine, but theequipment is expensive and may be available only at specialreferral facilities. Laser surgery provides precise removal ofthe cancer with minimal, if any, side effects. Finally, traditional surgical methods may be used to remove thecancer. The procedure is similar to ear cropping in dogs, inwhich part of the ear is removed with scissors and the skinedges are sutured together. In cats with squamous cell carcinomaof the ear tip, the veterinarian caring for the pet will removethe cancerous ear tip and about one-quarter inch ofnormal-appearing ear. A small amount of normal-appearing ear isremoved to ensure that the entire cancer has been removed. You should insist that a pathologist evaluate the excised tissueto make sure that the cancer has been completely removed. If thebiopsy shows that the cancer has not been completely removed,further surgery should be performed. Incomplete removal of thecancer at the initial surgery is not the fault of yourveterinarian. Microscopic evaluation of the tissue after specialprocessing is required to determine whether cancer cells arepresent in the tissue. The naked eye is not able to make thisdetermination. Cats tolerate the surgery well, and healing should progresswithout complication. The healed surgery area will have morehair than the ear tip, which will aid in preventing recurrenceof the cancer. Preventive care should be continued aftersuccessful surgery.In summary, prevention of precancerous actinic dermatitis isrecommended by limiting the outdoor activity of white orlight-colored cats to periods of nonpeak solar intensity.Appropriate sunscreens should be applied to the ear ofpre-disposed cats who are outdoors during periods of peak solarintensity. If your cat is diagnosed with actinic dermatitis, itshould be treated aggressively in the hope of preventing cancer. Progression of actinic dermatitis to squamous cell carcinomarequires surgery to remove the cancer. Because of availabilityand financial considerations, most cats with this form of cancerreceive treatment consisting of traditional surgery. Theappearance of your cat's ear after surgery will depend on theextent of the disease. The ear may simply appear rounded at thetip or require complete removal. If the entire ear is removed,your cat will still be loved and cute with a strikingresemblance to "E.T." of movie fame. Either result is far betterthan uncontrolled spread of cancer to deeper tissues of the head.The above is general veterinary information. Do not beginany course of treatment without consulting your regularveterinarian. All animals should be examined at least once every12 months.