Colorectal polyps in an Australian population. A histological and immunohistochemical study.

The histology and immunohistochemistry of 896 polyps and other focal epithelial abnormalities detected macroscopically in 86 surgical resections from patients with colorectal adenocarcinoma and benign bowel disorders were studied. The lesions identified included 177 adenomas, 387 hyperplastic (metaplastic) polyps, and 202 non-neoplastic polyps designated 'focal cryptal hyperplasia'. Numbers of both neoplastic and non-neoplastic polyps were significantly increased in resections for carcinoma, with 72 per cent of all polyps in right and 10 per cent in left hemicolectomy specimens being neoplastic. Thirty per cent of adenomas were less than 2 mm in diameter and 6 per cent larger than 10 mm. Observations on polyp size, number, distribution, histological appearance, and antigenic composition suggested that focal cryptal hyperplasia evolves into the hyperplastic polyp. In doing so, there is loss of expression of a tissue specific antigen. Hyperplastic polyps were significantly larger in colons with adenoma than in those without.