Angiogenesis in follicular tumors of the thyroid

Background: Experimental evidence suggests that tumor growth beyond a certain size and tumor ability to metastasize depend on the degree to which the tumor can stimulate an angiogenic response. Methods: Fifteen thyroid specimens of microinvasive follicular carcinoma were examined for vascularization by immunohistochemical stain with antifactor VIII antibodies and compared with an equal number of follicular adenomas. Results: Pleomorphic areas in the histological specimens of follicular carcinomas had a higher rate of vascularization as did areas of tumor adjacent to or penetrating the capsule. These features were not noted in follicular adenomas. Conclusions: Our findings indicate that vascularity may play a role in extracapsular extension and tumor aggression in follicular thyroid carcinomas.