Prostate cancer is the most prevalent cancer in western countries, being the third leading cause of male cancer death. To check its possible significance as a prognostic marker, allowing a better prognosis of the tumor, we analyzed the high-mobility group protein-A2 gene (HMGA2) expression level because HMGA2 overexpression has been shown to correlate with the malignant potential of various neoplasias. Aside from man, the dog is the only mammalian species that shows spontaneously occurring prostate carcinoma with striking similarities to prostate cancer growth and progression in man, making it an adequate animal model for this neoplasia. We used real-time quantitative reverse-transcription polymerase chain reaction for HMGA2 expression analyses in a subset of canine prostate tissue samples. Our investigations reveal that HMGA2 expression levels in all carcinomas were higher than those of any of the nonmalignant tissues. Thus, canine prostate cancer represents a spontaneously occurring model to test therapeutic effects resulting from reduced expression of HMGA2.