Today's Veterinary Practice

JAN-FEB 2016

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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com common neoPlasTic skin lesions in dogs & caTs Peer reviewed 32 treatment of choice is wide surgical excision. Depending on the area affected, such surgery may entail nasal planectomy or amputation of 1 to 2 digits. For cats with erosive lesions around their eyes, cryotherapy can be effective (Figures 9 and 10). Depending on the lesion size, liquid nitrogen may be applied with a cotton swab, cryoprobe, or cryospray device, using 2 to 3 freeze–thaw cycles. Protect the eye with ocular lubrication and use extreme care to avoid the cornea. 4 Basal Cell Tumor Description. With the advent of immunohistochem - ical staining, tumors can be reclassifed and renamed as they are investigated. This has occurred with basal cell tumors, one of the most common tumors in dogs and cats. The typical mass—benign, well-circum - scribed, and previously called basal cell tumor—is now recognized as a trichoblastoma (Figure 11). 5,6 The term basal cell tumor was also used as an umbrella term for a large heterogeneous group that included tumors from epidermal, trichofollicular, and adnexal tissues demonstrating basal cell characteristics. This is particularly relevant in cats, in which benign and malignant apocrine ductular sweat gland tumors and basal cell carcinomas are now recognized as having been lumped into the basal cell tumor category. These tumors have malignant potential and, although reports are limited, feline basal cell carcinomas are often highly metastatic. Additionally, while there are no reports of canine malignant basal cell tumors in the literature, veterinary oncologists, including this author, have seen rare cases of metastasis of basal cell tumors in dogs. Basal cell tumors arise in middle-aged to older dogs and cats, with some dog breeds, such as poodles, being over-represented. Diagnosis. Histopathology now differentiates among trichoblastoma, basal cell carcinoma, sweat gland tumors, and other epithelial tumors, but cytologists may still use the term basal cell tumor as a broad cytologic diagnosis covering all of these tumor types. The cytologic diagnosis of a tumor of basal cell origin is based on small, round to cuboidal cohesive cells arranged in tight clumps or ribbons (Figure 12, page 34). Features of malignancy may be recognized and support a diagnosis of carcinoma, but histopathology is needed to determine the tumor's malignant potential because the main criterion of malignancy is invasiveness. 7,8 Thus, once cytology confrms a tumor of basal cell origin, excision, followed by histopathology, is recommended whether or not cytologic features of malignancy are seen. FIGURE 9. Erosive SCC at the medial canthus of the left eye in a 12-year-old spayed female white domestic shorthair indoor/outdoor cat. Surgical excision of this type of lesion is not possible due to the diffuse and infltrative nature. FIGURE 10. Same cat as in Figure 9, 2 weeks after having the lesion treated with cryotherapy. The eschar will continue to recede and fall off within 1 to 2 weeks. Figure 11. A 4-mm raised hairless lesion on the lateral thorax of a 10-year-old spayed female Siamese cat, diagnosed as a trichoblastoma.

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