Abnormally proportioned gastric units and lack of terminal gland cell differentiation in large gastric Lkb1+/− polyps with characteristic Peutz-Jeghers features. A: Comparison of proliferating (Ki-67), foveolar (Alcian blue-Periodic acid-Schiff-; AB-PAS) and glandular cells (Griffonia Simplicifolia-lectin; GS-lectin) in antral mucosa of wild-type and Lkb1+/− mice, and in an antral polyp demonstrating a widening of the proliferating, foveolar (f), and glandular (g) zones in an antral Lkb1+/− polyp, at ×200 magnification. Scale bars = 100 μm. B: Staining of an antral polyp with desmin, GS-lectin, and AB-PAS demonstrates that GS-lectin positive gland-type cells are more abundant in the vicinity of desmin staining smooth muscle bundles (arrowheads). Micrographs recorded at ×100 magnification. Size bars = 200 μm. C: A fundic polyp demonstrating lack of pepsinogen C expressing zymogenic/chief cells and parietal cells (Hydrogen-potassium adenosine-triphosphatase; H+/K+-ATPase), whereas GS-lectin positive mucous neck cells (n) and foveolar cells (AB-PAS, arrowhead) are abundant. Inset in GS-lectin panel demonstrates that GS-lectin positive mucous neck cells (n) cover the gland base adjacent to the smooth muscle stalk (m), whereas in normal glands gland the base contains chief cells (c). The surface of this polyp had suffered an erosion (asterisks).