Alterations in the expression of cell-type specific gene sets in Lkb1+/− tissues, and the exclusion of spasmolytic polypeptide-expressing metaplasia in Lkb1+/− fundic polyps. A: Average fold change ± SD of gene expression in indicated cell-type specific gene sets including a random set for comparison (please see Materials and Methods) in Lkb1+/− polyps (black) and unaffected fundic mucosa (gray) compared with wild-type mucosa. P values indicate the statistical significance of the difference between the wild-type and the corresponding value, as given by the Student’s t-test. B: TFF2 and IF staining of Lkb1+/− fundic polyps and wild-type mucosa, demonstrating absence of IF in the polyp (upper row) at ×100, and a magnification of the area within the white box in the upper right panel. Scale bars = 200 μm. In the lower panels, micrographs at ×630 magnification (Scale bars = 32 μm) show fundic Lkb1+/− mucosa (left panel) and only TFF2-staining gland cells in the polyp proper (middle panel) as well as a gland with a single IF-positive cell from the border of a polyp base (right panel). C: Gastrin and chromogranin A (CgA) staining of Lkb1+/− antrum, fundus and a fundic polyp provide no evidence for antralization (antrum and fundus at ×200 magnification; polyp at ×100 magnification; Scale bars = 100 μm).