Fig. 2

Microscopic findings of resected tumor. a The common bile duct showed diffuse infiltration of lymphoid cells forming lymphoid follicles. The glands at the mucosal surface were extensively eroded by lymphocytic infiltration (hematoxylin-eosin (HE) ×40). b The neoplastic lymphocytes occasionally infiltrated into the glandular epithelium (lymphoepithelial lesion; HE ×400)