Prevalence of Mammary Gland Tumor of Small Breed Dog in the Tokyo Metropolitan Area.

Abstract

The present study investigated the prevalence of mammary tumors observed in small breed dogs mostly in Tokyo metropolitan area. The prevalence of mammary tumors was 7.9% on the whole, and prevalence was the highest (31.6%) in Miniature Schnauzer. Next, it was 13.9%, 13.0%, 12.7% and 9.8% for Maltese, in Shetland Sheep-Dog, Yorkshire Terrier and Pomeranian, respectively, concerning the breed of dogs. On the size of tumor, 3 cm or less in diameter were the common as 80.6% in the prevalence, and growing location was approximately twice as likely in the caudal glands of the 4th and 5th mammary glands compared to the cranial glands of the 1st to 3rd ones. Histopathologically, the prevalence of malignant tumor was high as 93.0% as, while benign tumor was 7.0%. Mixed-typed tumor of malignant and benign tumors was observed in 17.9%. Adenocarcinoma was observed in 37.3% in each case, intraductal papillary adenocarcinoma in 24.9%, malignant mixed tumor in 67.2%, benign mixed tumor in 22.9%, and malignant myoepithelioma in 1.5%. The histopathological characteristics of tumor were not associated with the breeds of dogs.