Slide 2.19
Low power view of a case of Hashimoto's thyroiditis. The majority of the thyroid parenchyma is infiltrated by a chronic inflammatory infiltrate (lymphocytes, plasma cells) forming lymphoid follicles with germinal centers. Residual thyroid is present in the left upper corner. Hashimoto's thyroiditis is an autoimmune disease. The lymphocytes infiltrating and destroying the thyroid parenchyma secrete anti-thyroglobulin and anti-thyroid peroxidase autoantibodies.

Slide 2.20
High power view of Hashimoto's thyroiditis showing lymphoid follicles within thyroid tissue. The arrow points to a germinal center. Note the small lymphocytes infiltrating between the follicular cells. The thyroid follicles are small, with no colloid, and the follicular cells have eosinophilic cytoplasm (Hürthle cells).