As the name suggests, this is an inflammatory disease of the thyroid. The leukocytic infiltrate is almost entirely lymphocytic. No germinal centers are seen. Notice in this slide the large number of lymphocytes. In fact, the only clue that this is thyroid is the small number of cords of follicular cells without follicles and without colloid. Nonetheless, knowing that this specimen is from a painless enlarged thyroid, together with this microscopic presentation, allows for an accurate diagnosis. The etiology of this disease is enigmatic, mysterious, cryptogenic and even perhaps idiopathic.