Case report: Compact cellular (solid) carcinoma containing Hurthle cell areas in the thyroid gland of a dog

A 7-year-old Collie dog was referred to the clinics of the department of surgery of the veterinary faculty of Istanbul University with a complaint of swelling in the neck, suggesting a thyroid disease. Two separate masses, located at the upper and median 1/3 parts of the neck were detected at physical examination and were surgically removed. Grossly, encapsulated solid masses (4x3x2cm(3) and 2x1x1cm(3)) with lobular, haemorrhagic and greyish-white cut surfaces were detected. Histological examination revealed wide, eosinophilic polygonal cells with tiny cytoplasmic granules and centrally localized prominent nuclei. Smaller cells forming insular structures along with cell clusters that constituted fusiform bundles were observed, as well. In some fields, follicles containing colloid matrix were remarkable. The masses were diagnosed as follicular compact cellular carcinoma containing Hurthle cell areas that are rarely described in dog thyroid carcinomas