Fig. 2.

Vascular invasion (VI): Schematic drawing for the interpretation of the presence or absence of VI. The diagram depicts a follicular neoplasm (green) surrounded by a fibrous capsule (blue). a Bulging of tumor into vessels within the tumor proper does not constitute VI. b Tumor thrombus covered by endothelial cells in intracapsular vessel qualifies as VI. c Tumor thrombus in intracapsular vessel considered as VI since it is attached to the vessel wall. d Although not endothelialized, this tumor thrombus qualifies for VI because it is accompanied by a fibrin thrombus. e Endothelialized tumor thrombus in vessel outside the tumor capsule represents VI. f Artefactual dislodgement of tumor manifesting as irregular tumor fragments into vascular lumen unaccompanied by endothelial covering or fibrin thrombus. Modified from: Chan JKC Reprinted with permission [3]