Invasive adenocarcinomas in animals in tumor study. (A-C) H+E-stained (A: low-power view; B: high-power view) and SMAimmunostained(C) histologic sections of a representative invasive tumor. Note neoplastic epithelium invading through the muscularis propria (mp) of the intestinal wall (solid arrowheads) and into the outermost serosa layer (s and open arrowheads; m: mucosa; SMA immunostain highlights well-oriented muscularis propria layer). (D-G) Histologically aggressive lesions. H+E-stained (D: lowpower view; E: high-power view) histologic sections showing poorly formed glands and clusters of neoplastic epithelial cells (asterisk in D and arrow in E) in a densely collagenized desmoplastic stroma. These aggressive lesions express high-levels of cytoplasmic and nuclear beta-catenin (arrowhead in F; inset: detailed view), but retain membranous E-cadherin expression (arrowheads in G; inset: detailed view).