FIG. 1.

Microphotographs of papillary thyroid carcinoma (PTC), classical type with vascular invasion (hematoxylin and eosin slides). (A) Low-power view of the carcinoma showing papillae (arrow). (B) On high power, the papillae are covered by cells with enlarged, clear, irregular, overlapping nuclei with grooves (arrow). This nuclear atypia is diagnostic of PTC. (C) Low-power view showing a tumor thrombus (TT) hanging in the lumen of a medium-sized extrathyroid vessel (delineated by arrows) located immediately outside the thyroid capsule. (D) High-power view of the tumor thrombus (TT) in (C) covered by endothelial cells (arrow).