Figure 7. Microscopic findings of the peribiliary glands (PBGs). Two representative sections of the bile duct wall with few invasive cancer components (A–C and D–F) show the bile duct lumen and intramural PBGs using serial sections (A corresponds to B, and D to E). Immunohistochemical study using anti-laminin antibody delineating the basement membrane of the PBGs and glandular canals (A and D). Vessels are also delineated more clearly. The hematoxylin and eosin-stained specimens in the mid-power field show the relationship of the intramural PBG and the adenocarcinoma (B and E). The specimens in the high-power field (C and F, magnified image of the yellow square in B and E, respectively) show the in situ-like carcinoma cells that extend, replacing the epithelium of the PBG. The epithelium of most of the PBGs and glandular canals is replaced by carcinoma cells (B and E, yellow arrow head), whereas some intact PBGs are seen (white circle). The carcinoma cells in the bile duct lumen are hardly seen in these specimens. Drawings schematically show a cross-section (G) and a longitudinal section (H) of a segment of the extrahepatic bile duct containing both intramural and extramural PBGs. The observed distribution of the carcinoma cells in this case is shown by the red lines.