Canine thyroid neoplasms: epidemiologic features.

A retrospective study of medical records from twelve veterinary university hospitals-clinics yielded 144 dogs with a confirmed diagnosis of a thyroid neoplasm (25 adenomas and 119 carcinomas). Forty-five of these dogs had additional primary neoplasms. As in man, associated tumors suggested the inherited multiple endocrine adenomatosis, type 1, and a possible syndrome of thyroid and chemoreceptor lesions. Although the female preponderance of human thyroid cancer was not seen in dogs, females showed a much sharper increase in risk with advancing age than did males. Three breeds (beagle, boxer, and golden retriever) had a significantly greater risk for thyroid carcinoma than did all dogs combined, whereas miniature and toy poodles had a low risk. The function of thyroiditis in the origin of thyroid cancer, as suggested by reports of thyroid carcinoma in people with Hashimoto's disease, may be clarified by follow-up studies of beagles which are prone to Hashimoto-type thyroiditis.