Stomach and colon polyp formation in Smad4^Δ/Δ mice. The left panel shows a Smad4^fl/fl control mouse, right panel shows a Smad4^Δ/Δ mouse. Gross macroscopy of stomach (A,B), histologic hematoxylin-eosin staining of stomach (C-F), and colon (G-J) with magnified view of the boxed areas. Magnifications for A,B: 2.5×; C,D: 50×; E-H: 100×; I,J: 200×.