Figure 2.

Histopathologic characterization of endolymphatic sac tumor. A. Histologic sections showed a papillary architecture (H&E, 100×). B. The stroma of the papillary fronds was richly vascularized(H&E, 200×). C. The papillary structures were lined by a single layer of flattened cuboidal-to-columnar cells. There were minimal cellular pleomorphism and rare mitotic activity (H&E, 400×). D. There were cystic glandular spaces filled with colloid-like material which was remarkably similar to thyroid tissue (H&E, 200×).