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THE PET HEALTH LIBRARY
By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com

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Squamous Cell Carcinoma in Cats

A squamous cell carcinoma. Photo by MarVistaVet

There isn't really any good way to get a squamous cell carcinoma. The tumor is locally destructive and spreads aggressively in the area where it has arisen. That said, there are some circumstances where it is possible to either cure or achieve meaningful control of this tumor and the nasal form is one of these situations.

The squamous cell carcinoma is associated with sun exposure, and this means that lesions on the white-furred areas of the feline face are at risk. The ear tips and nose are particularly vulnerable, as one might expect as these areas are not well-protected by fur.

The squamous cell carcinoma begins as a small scabby area that may not attract much attention as it can be mistaken for a minor abrasion. This minor abrasion, however, does not heal and continues to get larger.

Because the squamous cell carcinoma does not spread distantly in the body until late in its course, this provides a window during which it can be successfully treated. Once it gets too big, that window has closed even if the tumor has not yet spread.

Surgical Treatment

If the tumor is not too big, surgical removal is curative. The squamous cell carcinoma is invasive so a wide margin of normal tissue must be excised in order to get the whole tumor. If the tumor has been allowed to grow too large, there will not be enough tissue to get a good margin around it and it will regrow, resuming its destructive course.

The surgery is ideally done with laser equipment to reduce bleeding; it is probably best to seek the skills of a surgery specialist or at least a veterinarian with a great deal of facial surgery experience. Discuss with your veterinarian whether or not a referral to a special is in the best interest of you and your pet.

The leather of the nose is removed along with some of the surrounding haired skin. The nasal opening will heal cosmetically but will look a little unusual.

Cryotherapy may be less invasive. This involves using a probe to freeze the tumor. Again, this can be curative if the tumor is small enough but in freezing the tissue, there is no tissue to send to the lab for analysis. The biopsy (lab analysis) of the tissue not only confirms squamous cell carcinoma but also enables the pathologist to tell if the excision was complete or not. This is valuable information which we would prefer not to forgo for obvious reasons.

Radiation Therapy

Radiotherapy is rapidly becoming treatment of choice. Strontium plesiotherapy using strontium 90 involves applying a localized radiation source to the tumor directly for a brief period of time. (Imagine a wand with a radiation source on the end.) Radiation destroys tissue in a 3 mm diameter from the source, which allows for the destruction of small superficial tumors. As with surgery, if the tumor is too big, it cannot be cured.

Alternatively, external beams of radiation can be aimed at the tumor under general anesthesia. In one study, 60 percent of irradiated cats had a complete response and 33 percent had a partial response.

Radiation therapy obviously requires specialized equipment that is usually found only in specialty facilities. It is not available everywhere. A consultation with a veterinary oncologist will help determine if a given patient is a good candidate and what is involved in finding the nearest radiofacility.

Imiquimod 5% Creme

Imiquimod is a an immunity-modifying topical crème that is palliative for tumors too large for curative removal, or to treat the more superficial form of squamous cell carcinoma called Bowenoid carcinoma or squamous cell carcinoma in situ. Imiquimod is a relatively expensive product and upset stomach can result if the crème is licked (which it inevitably would be). See a video of its use.

Other Ideas

There is some thinking that carcinomas express enough cyclooxygenase that a non-steroidal anti-inflammatory pain reliever (such as piroxicam, meloxicam, or robenicoxib) may have anti-tumor effects. There is a great deal of controversy over this and these medications are not without issues in feline patients. That said, pain relief is important for an invasive tumor such as a facial squamous cell carcinoma.

Even though the squamous cell carcinoma does not spread until relatively late in its course, it is still extremely difficult to address. The nasal version is somewhat of an exception to the poor prognosis rule as long as it is detected early and removed or irradiated promptly.

 

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