Squamous cell carcinoma

From Cat
Nasal actinic keratitis (precursor SCC) in a 13-year-old Domestic shorthair cat. Courtesy Dr Jim Euclid
SCC on the nasal planum of an 21-year-old Domestic shorthair cat that failed to respond to two courses of radiation therapy and local surgical excision. Courtesy of Dr Jim Euclid
Cat above, 2 years later, prior to euthanasia. Courtesy Dr Jim Euclid
File:Scc2.jpg
Bilateral squamous cell carcinoma of the pinna in a white Domestic shorthair cat

Squamous cell carcinomas (SCCs), are a relatively common cancer of cats, affecting the ears, nose and eyelids of cats. It occurs more frequently in white cats, but is seen in other bi-color and tortoiseshell cats, especially when there is little or no pigment in these areas.

Actinic keratosis, a prequel to this form of epidermal carcinoma, are plaque-like to papillated, solitary or symmetrical, scaly lesions. Clinical identification of these lesions are important in annual health checks, since they are good prodromal indicators of a high risk for SCC development in later years of the cat's life.

SCCs are caused by a number of factors, including:

  • Pigment deficits - most SCCs occur in white cats or non-pigmented regions of skin
  • UV radiation - exposure to sunlight is the biggest risk factor, especially during midday hours.
  • Viral - feline SCCs often contain feline papillomavirus type 2 DNA, although a cause and effect relationship between the two has never been proven[1][2]. Infection by feline immunodeficiency virus (FIV) is associated with high rates of feline SCC development, possibly due to increased papillomavirus infection.

Feline bowenoid in situ carcinoma is a rare variant of this disease.

Clinical signs are relatively obvious, with reddened and crusty skin at the tips of the ears, the nose and around the margins of the eyelids. Quite often scabs will appear in these areas as well, and because the region is often pruritic, the cat will be seen scratching the area, and bleeding often results.

Treatment of squamous cell carcinomas in cats usually is conservative in early cases, and surgical in advanced cases. Caution must be noted when treating nasal SCCs as these are best treated early with surgical intervention as invasion of nasal septal tissue is common, requiring often disfiguring rhinectomy.

Cryosurgery is a relatively simple procedure to perform and not expensive. Recurrence is quite common and necessitates yearly treatment.

Radiation therapy, which is now being adopted as a more common procedure has much higher success rates in terms of long term cures. Although expensive, radiation therapy offers the advantages of being non-invasive and with fewer side-effects compared with cryosurgery or surgical amputation.

Since the majority of SCCs are caused by ultraviolet rays in sunlight, keeping the cats indoors during the hours of 10:00 am and 3:00 pm are important.

References

  1. Munday, J.S., Dunowska, M & de Grey, S (2009) Detection of two different papilloma viruses within a feline cutaneous squamous cell carcinoma: case report and review of the literature. N Z Vet J 57(4):248-51
  2. Munday JS, Witham AI. (2009) Frequent detection of papillomavirus DNA in clinically normal skin of cats infected and non-infected with feline immunodeficiency virus. Vet Dermatol Dec 23