| Ectopic
thyroid tissue was identified at the base of the tongue in a 9-year-old,
euthyroid, domestic shorthair cat. The lingual submucosa and the muscles
were replaced by thyroid tissue, which consisted of various-sized follicles
each lined by a row of cuboidal epithelium. Many follicles contained eosinophilic,
periodic acid Schiff-positive, colloid material. Immunohistochemically,
the epithelial cells stained positive for AE1 /AE3 and thyroglobulin.
No calcitonin positive cells or parathyroid tissue was seen. The cat has
been followed for 1,018 days after surgery, is clinically well and remains
euthyroid. |