Expression of vascular endothelial growth factor (VEGF) in human thyroid tumors.

Vascular endothelial growth factor (VEGF) is one of the factors related to angiogenesis of tumors and physiological and pathological proliferative processes. Location of VEGF in human thyroid tissue with various thyroid disorders was studied in order to explore its possible involvement in proliferative processes. Immunohistochemical examination was performed on 69 formalin-fixed, paraffin-embedded thyroid tissue specimens using the labelled streptavidin biotin peroxidase complex detection system. VEGF was not identified in normal thyroid follicular cells. Some but not all tumor thyreocytes expressed VEGF in cytoplasm. VEGF positive expression was found in 6/15 patients with papillary carcinoma, 4/9 with follicular carcinoma, 14/28 with follicular adenoma and 2/17 with adenomatous goiter. In benign follicular adenoma and adenomatous goiter the weak expression of VEGF was found in small areas of the tumor tissues, whereas in malignant tumors it was found strongly in many cells. VEGF probably functions as a hypoxia-inducible angiogenic factor, and the expression of VEGF is stronger in malignant tumors, which need more oxygen supply to proliferate. An intensive VEGF production by differentiated thyroid carcinomas could be a promising marker of tumor aggressiveness and may also be useful as a predictor of metastatic potential and extension of tumor mass.