Electron microscopic and immunohistochemical studies on Hashimoto's thyroiditis.

Three types of Hashimoto's thyroiditis, lymphoid type (L-type), oxyphilic epithelium (O-type) and pronounced epithelial destruction (p-type), were ultrastructurally and immunohistochemically studied. In both the L-type and the O-type, two different kinds of follicles, active and degenerated ones, were ultrastructurally found. Although the follicular conformation was generally conserved, focal basement membrane damage was frequently found around the generated follicles. Some plasma cells and lymphocytes transversed the basement membranes and could be seen in the spaces between adjacent epithelial cells. In the P-type, most epithelial cells were replaced by fibrillar fibrous bundles, and destructive products probably derived from epithelial cells were scattered in the stroma. Immunoglobulin (IgG, IgA and IgM) deposittions was found not only in some basement membranes, colloid, epithelial cells and peeled-off cells in the follicles but also in the stroma. Some of the infiltrating plasma cells and lymphocytes had immunoglobulins in the cytoplasm. The intensity o the positive staining was by far the strongest for IgG, and the number of immunoglobulin-containing immunocytes was also the largest for IgG.