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23 Cancer Biology in Dogs

Chand Khanna, Melissa C. Paoloni


The recent availability of the dog genome sequence has contributed, and will continue to contribute, to our understanding of canine physiology, pathophysiology, and disease. This may be most true for the problem of cancer in dogs. It has been estimated that there are approximately 65 million pet dogs at risk of developing cancer in the U.S. (Vail and MacEwen 2000). Twenty-three percent of all dogs, regardless of age, and 45% of dogs 10 years of age or older die of cancer (Withrow and MacEwan 2001). Estimates of age-adjusted cancer incidence range from 243 to 381 per 100,000 dogs/year at risk (Bronson 1982). These rates are comparable to those reported by the National Cancer Institute SEER program for human beings (~300 per 100,000) (Dorn and Taylor 1968; Priester and McKay 1980; Bronson 1982; Khanna and Vail 2003). Cancers in dogs share many of the basic biological features of human cancers and cancers of other species. Interestingly, the spectrum of cancer histologies seen in the dog does not completely mirror those seen in humans. Whereas humans most commonly develop carcinomas (breast, prostate, and lung cancer), dogs more commonly develop lymphoma, sarcomas, and then carcinomas.

Cancer in all species is strictly defined as an uncontrolled growth (or proliferation) of cells that results in an abnormal accumulation of cells in a particular region of the body. A tumor is the mass that results from this abnormal proliferation of cells within a tissue. Transformation of a normal cell into a phenotypic cancer cell involves a...

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