A10ΔEC mice develop intestinal polyps. (A-D) H&E staining of intestine from an A10ΔEC (A-B) and control (C-D) mouse revealed hyperplastic intestinal polyps (indicated by arrows in panel A) with marked hypercellularity within the lamina propria of A10ΔEC individuals (marked by arrows in panel B). (E-F) Almost all cells within the lamina propria of the enlarged polyps in A10ΔEC intestine stained positively for MECA-32 (E, arrow), while less than half the cells were MECA-32–positive in the corresponding area in control villi (F). Please note that the round dark-staining cells marked by arrowheads most likely represented plasma cells and not endothelial cells. Scale bars in panels A,C: 500 μm; B,D-F: 20 μm.