• 24 APR 14
    • 0

    Squamous-cell carcinoma

    On radio, television and in the printed media we humans are constantly warned about the dangers of exposure to the harmful rays of the sun. We are warned to cover our skin, avoid direct sunlight especially during the middle of the day and to apply sun block when we do expose ourselves to the sun. This serves to prevent the formation of skin cancer in later life. Well, the same rules should apply to cats. Most cats are lucky: The skin is covered with hair that block out the harmful rays and the hairless areas are usually protected by pigment in the skin. However, just as fair-skinned people are more prone to sunburn, so fair skinned cats are more prone to sunburn. White cats and other cats with white body parts are most likely to develop problems. The most susceptible areas in these cats to cancer formation are the ear tips, eyelids and the tip of the nose.

    With chronic excessive exposure to the sun, the white or hairless parts of the skin initially get sunburnt and may later develop precancerous changes known as actinic dermatitis. This may be visible especially in the older cat (and especially in cats that enjoy basking in the sun) as flakiness, crustiness and mild hair loss of the ear tips or nose. If left untreated, these areas will eventually become cancerous, the most common cancer being squamous-cell carcinoma. The cancerous lesion may be recognised as ulceration or destruction of the normal tissue, very often covered with a crust. This may look like a wound that is slow to heal. Usually a small tissue sample must be obtained and analysed to confirm the diagnosis and determine whether the lesion is cancerous or precancerous. This is the best time to effectively treat the condition to prevent it becoming cancerous.

    The precancerous lesions can be treated by restricting further exposure to the sun, the application of sunscreens and freeze therapy (cryotherapy). Once the area has become cancerous, medical therapy is no longer effective. Cryotherapy and surgical removal of the ear tips or nose is then the most effective treatment and should be performed early, as soon as the problem is discovered. The earlier surgery or cryotherapy is performed, the smaller the amount of ear or nasal tip that must be treated or removed and the less likely that spread of the cancer may have occurred. In some cases, the entire ear and ear canal may need to be removed to prevent spread of the cancer. It is always safer to remove too much tissue rather than too little. With cryotherapy, freezing of the affected areas is performed. This kills off abnormal and also some normal tissue, whereafter the body will heal the wound. This can be very effective, but it may be difficult to control the amount of tissue loss. If the lesion is left untreated too long, the affected area may be too deep for cryosurgery to be effective, especially on the tip of the nose. Lastly, in some cases and where available, radiation treatment of cancerous lesions can be performed. This type of treatment again results in no systemic side-effects. Once surgical treatment, cryotherapy, chemotherapy or radiation has been performed, it is important to limit further exposure to the sun. Continuous sun-exposure will result in recurrence of the cancer. Tattooing or injection of die into the skin is not effective to prevent cancer and is no longer performed.

    To summarise, the approach should be: Limit exposure to sunlight, apply sunscreen, and be observant. The earlier a problem is discovered, the more effective it can be treated and the less impact it will have on your cat. Early treatment is not only safer, it is also less costly. Early and aggressive surgery or cryotherapy is strongly recommended. Do not be scared of aggressive surgical removal of affected parts, as this may save the cat’s life. And remember, once treated, avoid further excessive sun exposure.

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