Figure 3b. Early-stage Hashimoto thyroiditis in a 42-year-old woman who presented with goiter as well as firmness of the right thyroid lobe. Laboratory values were as follows: T4 = 7.6 µg/dL, T3 = 121 ng/dL, and TSH = 5.5 µIU/mL. The 24-hour RAIU was mildly elevated at 39%. (a) Anterior scintigram demonstrates an enlarged thyroid with diffusely increased radiotracer uptake (high target-to-background activity), findings that are similar to those in a diffuse toxic goiter. Note the decreased background activity as shown by the low radiotracer concentration in the salivary glands (thin arrow). The photopenic area (thick arrow) represents the cold sternal marker. (b) Photomicrograph (original magnification, x150; H-E stain) of a histologic specimen obtained during open biopsy of the right lobe reveals dense lymphocytic infiltration with reactive germinal centers (arrow).