Fig. 2

Immunohistochemical findings of (a) lower pole’s mass, (b) background tissue in the thyroid, and (c) the regional lymph node. Numerous CD138⁺ plasma cells were infiltrated in the lower pole’s mass, background of thyroidal tissue, and regional lymph nodes. Most were IgG-secreting plasma cells, and 40–50% of them were IgG4-secreting cells. Bar = 50 μm