Immunohistochemical staining for claudin-7 in colorectal adenomas, carcinomas and adjacent normal tissue. The top four pictures are taken from an individual with dysplasia but no record of carcinoma and the bottom four pictures are from a patient with colorectal cancer. A) Tissue section including both normal mucosa and dysplastic tissue, stained with PAS/Alcian. B) Neighbouring tissue section stained for claudin-7. The white arrow indicates mucosa of normal appearance and the black arrow indicates dysplastic tissue. C) High magnification of the normal mucosa from B, showing staining mainly at the basolateral cell membranes of the epithelial cells. D) High magnification of the dysplastic tissue from B showing a patchy staining pattern with areas of low and normal staining. E) Tissue section with cancerous tissue to the right and normal mucosa to the left, stained with Hematoxylin and Eosin. F) Neighbouring tissue section stained for claudin-7. The white arrow indicates the mucosa with normal appearance. The black arrow points out carcinomatous tissue. G) High magnification of histologically normally appearing mucosa from F, showing staining mainly localised to the basolateral cell membranes of the surface epithelial cells. H) High magnification of carcinomatous tissue showing faint, patchy staining of the epithelial strands of tumour tissue. Scale bars: 500 μm (A + B + E + F), 100 μm (C + D + G + H).