Max's House
Solar-Induced Squamous Cell Carcinoma in Cats
Mark M. Smith
Squamous cell carcinoma is a cancerous disease that most commonly involves skin.
Fair-skinned people tend to be predisposed to this type of cancer after chronic, excessive
exposure to sunlight. Likewise, white or light-colored cats are also susceptible to
squamous cell carcinoma. Solar-induced squamous cell carcinoma usually occurs in areas
with little hair coverage that are chronically exposed to sunlight. The most common area
affected in cats is the ear tip. This disease occurs in older cats and may first become
apparent in summer, when sunlight exposure is greatest.
Symptoms may include the following:
- Reddening of the
ear tip (likely to be first symptom)
- Mild hair loss
and flaking of skin on the ear tip
- Scale and
inflamed skin, as with psoriasis
If caught early, these clinical signs may
be indicative of the precancerous form of the disease known as actinic dermatitis. A small
skin biopsy is required to differentiate precancerous actinic dermatitis from squamous
cell carcinoma. It is best to perform the biopsy procedure early because the clinical
lesions of squamous cell carcinoma are subtle and similar to this form of dermatitis. One
or both ears may be affected. If only one ear is diseased, the other should be monitored
closely because it may also acquire the disease in the future.
Early, effective treatment of precancerous
lesions may prevent the onset of squamous cell carcinoma. Treatment for actinic dermatitis
includes the following
- Sun restriction,
especially during times of peak solar intensity
- Water-resistant
sunscreens with sun protection factor (SPF) 15 or greater applied to the ear tips twice
daily
- Topical steroid
application
- Possibly oral
steroid or anti-inflammatory therapy
The drug etretinate also may be used to alleviate symptoms. The
effect of etretinate is to decrease inflammation and skin flaking while normalizing skin
cell metabolism. Medical therapy is not effective for lesions that advance to squamous
cell carcinoma, which underlines the importance of early diagnosis for suspicious lesions.
Surgical removal of squamous cell carcinoma of the ear tip
(partial pinnectomy) is most effective when performed as soon after diagnosis as possible.
Early intervention decreases the amount of the ear that must be removed, because the
lesion is smaller. Early surgical removal also decreases the incidence of spread of the
cancer to the lymph nodes near the ear.
Different surgical methods are effective in removing the
cancer:
- Cryosurgery,
like frostbite, freezes the ear tip. The frozen tissue dies and is removed. Although this
method may be effective, it is sometimes difficult to control the precise area of tissue
freezing. Freezing an inadequate area may lead to recurrence of the cancer, and excessive
freezing may result in an unsightly appearance and be associated with excessive scar and
deformation of the remaining ear.
- Laser surgery
is available in veterinary medicine, but the equipment is expensive and may be available
only at special referral facilities. Laser surgery provides precise removal of the cancer
with minimal, if any, side effects.
- Traditional
surgical methods may be used as well. The procedure is similar to ear cropping in
dogs, in which part of the ear is removed with scissors and the skin edges are sutured
together. In cats with squamous cell carcinoma of the ear tip, the veterinarian caring for
the pet will remove the cancerous ear tip and about ¼ inch of normal-appearing
ear. A small amount of normal-appearing ear is removed to ensure that the entire cancer
has been completely removed.
If the biopsy shows that the cancer has not been completely
removed, further surgery should be performed. Incomplete removal of the cancer at the
initial surgery is not the fault of your veterinarian. Microscopic evaluation of the
tissue after special processing is required to determine whether cancer cells are present
in the tissue. The naked eye is not able to make this determination.
Cats tolerate the surgery well, and healing should progress
without complication. The healed surgery area will have more hair than the ear tip, which
will aid in preventing recurrence of the cancer. Preventive care should be continued after
successful surgery.
In summary, prevention of precancerous actinic dermatitis is recommended by the
following:
- Limiting the
outdoor activity of white or light-colored cats to periods of nonpeak solar intensity
- Applying
appropriate sunscreens to the ear of predisposed cats who are outdoors during periods of
peak solar intensity
If your cat is diagnosed with actinic dermatitis, it should be
treated aggressively in the hope of preventing cancer. Progression of actinic dermatitis
to squamous cell carcinoma requires surgery to remove the cancer. Because of availability
and financial considerations, most cats with this form of cancer receive treatment
consisting of traditional surgery.
The appearance of your cat’s ear after surgery will depend on
the extent of the disease. The ear may simply appear rounded at the tip or require
complete removal. If the entire ear is removed, your cat will still be loved and cute,
with a striking resemblance to “E.T.” of movie fame. Either result is far better
than uncontrolled spread of cancer to deeper tissues of the head.
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