Cytomorphologic aspects of thyroiditis. A study of 51 cases with functional, immunologic and ultrasonographic data.

Fine needle aspiration provided material for detailed cytomorphologic study in 51 cases of thyroiditis, 40 of which were diagnosed as Hashimoto's (autoimmune) thyroiditis. Of these 40 cases, 22 were found to be euthyroid on clinical examination and radioimmunoassay (RIA), 10 were hyperthyroid and 8 were hypothyroid. Of the 11 cases of subacute thyroiditis, 4 were thyrotoxic and 7 were euthyroid. Radioactive iodine uptake (RAIU) showed decreased to negligible uptake in ten and normal uptake in one case of subacute thyroiditis, whereas all of the thyrotoxic cases of Hashimoto's thyroiditis showed markedly increased RAIU. Echography showed a hypoechoic or anechoic pattern in most of the cases. Antimicrosomal and/or antithyroglobulin antibodies were positive in 25 cases of Hashimoto's thyroiditis and in 1 case of subacute thyroiditis. The cytologic features that characterized subacute thyroiditis were the presence of multinucleated giant cells and a polymorphonuclear and lymphocytic population associated occasionally with epithelioid-cell granulomas. Hashimoto's thyroiditis was characterized by Hürthle-cell changes and a significant lymphoid population consisting of mature and transformed lymphocytes, often impinging on follicular cells. There was an overlap in the cytomorphologic features between some cases of Hashimoto's and subacute thyroiditis. In such cases, the final diagnosis was arrived at by an integrated approach incorporating all of the diagnostic parameters available.