Immunohistochemical localization of acidic and basic fibroblast growth factors in human benign and malignant thyroid...

The localization of acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) was investigated immunohistochemically in human benign and malignant thyroid lesions. Immunostaining for aFGF and bFGF displayed diffuse or granular deposits of the reaction products in the cytoplasm of neoplastic cells, especially in the marginal region of follicular adenoma, follicular carcinoma and papillary carcinoma. All lesions except for diffuse hyperplasia, which was completely negative in immunostaining for all antibodies, showed an increased immunostaining for bFGF (Ab-1) over that of aFGF and bFGF (Ab-2). Basement membranes of follicular and papillary structure and the fibroblasts located in the stromal tissues were free from immunostaining for all antibodies. The ratio of positive immunostaining for all antibodies was highest in papillary carcinoma, with an incidence of more than 80.0%, followed, in descending order, by widely invasive follicular carcinoma, minimally invasive follicular carcinoma, follicular adenoma and normal thyroid, in which some follicular cells exhibited weak reaction products. aFGF with a molecular weight of 18 kDa was identified in papillary carcinoma of the thyroid. From these data, we concluded that aFGF is synthesized in the neoplastic follicular cells of the thyroid, and aFGF and bFGF may have important roles in the neoplastic proliferation of follicular cells.