Figure 8. Immunohistochemical study using anti-E-cadherin antibody. The hematoxylin and eosin-stained specimen of bile duct wall in the mid-power field (A) shows both the in situ-like carcinoma cells that extend, replacing the epithelium of the peribiliary gland (PBG; red and yellow circles) and intact PBGs (white circle). Immunohistochemical study using anti-E-cadherin antibody of this specimen using serial section (B) shows that the epithelial cells of the PBG are positive for E-cadherin in an apicolateral pattern (white circle). In contrast, the expression of E-cadherin decreases in carcinoma cells (red and yellow circles), and the decreasing trend is stronger in the deeper region (yellow circle) than in the shallow region (red circle). The hematoxylin and eosin-stained specimens in the high-power field of the intramural (C) and the invasive portion of outside the bile duct wall (E) show carcinoma cells in which the expression of E-cadherin is decreased in the intramural region (D) and is lost in the invasive portion (F) on the immunohistochemical study using anti-E-cadherin antibody.