RESUMEN
A case of thyroid Rosai-Dorfman disease (RDD) without apparent lymphadenopathy in a 49-year-old woman with underlying euthyroid chronic autoimmune thyroiditis, as indicated by high thyroid autoantibodies titers, is presented. The initial presentation was that of a cold, hypoechogenic nodule of left thyroid lobe which increased in size during the two years of follow up, together with new ultrasonographic findings of the right lobe. No biochemical abnormalities were found apart from mild hypercalcemia. A near total thyroidectomy was performed. Histologically, the left lobe nodule as well as the right lobe lesions consisted of typical RDD cellular population, with the pathognomonic phenomenon of emperipolesis. Infiltration to the periphery of the gland was observed and three adjacent lymph nodes were also involved. The uninvolved thyroid parenchyma showed changes compatible with chronic autoimmune thyroiditis. No other localizations or systemic manifestations of RDD were revealed. Normocalcemia was restored promptly and the patient remains free of clinically overt disease one year post-operatively.