Figure 6b. Hashimoto thyroiditis manifesting as a solitary cold nodule in a 34-year-old woman who complained of a palpable right-sided neck mass of 5 months duration. At physical examination, the nodule felt very firm. Thyroid function parameters were all in the normal range, and the 24-hour RAIU was 22%. (a) Anterior image reveals a large, cold nodule in the right lower pole (arrow). A partial right lobectomy was performed to remove the nodule because of its firmness. (b) Photomicrograph (original magnification, x150; H-E stain) demonstrates Hashimoto thyroiditis.