Fig. 5

Elastica van Gieson staining and S-100 immunostaining. The duodenal papillary common channel was investigated with HE staining (a ×12.5), Elastica van Gieson staining (b ×12.5; d ×100), and S-100 immunostaining (c ×12.5; e ×100). a The IAPN (arrow) pervading in the common channel (asterisk) was transformed to the mucinous adenocarcinoma which invaded to the stroma of Vater papilla extensively (arrowhead). d Elastica van Gieson staining (high-magnification image of square in b) showed cancer cells (arrow) inside elastic tissues in the vein wall (arrowhead), indicating venous invasion. e S-100 immunostaining (high-magnification image of square in c) showed mucous nodes (arrow), adjacent to a nerve fiber bundle (arrowhead), indicating perineural infiltration