Fig. 3

Pathological findings. Hematoxylin-eosin stained histologic sections of the resected perihilar bile duct. The tumor cells were arranged in the cellular nests and cords infiltrating the bile duct wall. The mucosa epithelium was mostly eroded (upper right) (a: ×100). The tumor cells were round or oval with scant cytoplasm. Numerous mitotic figures and apoptotic bodies are noted (b: ×400). In the immunohistochemical studies, the tumor cells were diffusely positive for synaptophysin (c: ×400), and CD56 (d: ×400). Approximately 70 % of the tumor cells were positive for Ki-67 (e: ×400)