S-100 protein-positive dendritic cells in follicular lesions of the thyroid

Little is known about the role of S-100 protein-positive dendritic cells in follicular lesions of the thyroid. In 36 cases of adenomatous goitre, Is cases of follicular adenoma, and 7 cases of follicular carcinoma, we investigated the incidence and distribution of S-100 protein-positive dendritic cells using immunohistochemical staining. Four cases (10.5%) of adenomatous goitre, five cases (31.3%) of follicular adenoma. and 6 cases (85.7%) of follicular carcinoma contained S-100 protein-positive dendritic cells in the subcapsular area and/or the hyalinized stroma. Dendritic cells in the subcapsular area were observed only in lesions with thick capsules and not those with thin capsules. In most cases of follicular carcinoma, ++ to +++ of the dendritic cells was seen together with a few lymphocytes and fibroblasts in the subcapsular areas. In contrast, cases of adenomatous goitre and follicular adenoma showed only a few dendritic cells without any inflammatory cells. Dendritic cells in follicular thyroid lesions may play some role in capsular formation or may be a secondary phenomenon due to capsular formation.