A case report and review: the gross, histological and immunohistochemical characteristics of a carcinoma of ectopic thyroid in a dog.

Neoplasms of the canine thyroid gland represent 5-10% of heart base masses (Capen, 1978). Ectopic thyroid tissue is detected most commonly in the thorax, with 23-80% of all dogs having ectopic tissue at the base of the heart (Leav et al., 1976; Walsh & Diters, 1984). We describe here the gross and microscopic features of a rare ectopic thyroid carcinoma in a dog and the results of an immunohistochemical study of the tumour.