[Hyperplastic colorectal polyp: histological, histochemical and immunohistochemical study of 43 cases].

Forty-three solitary hyperplastic polyps removed from the colon or the rectum (HPC) were examined under light microscopy. A histochemical and immunohistochemical study was undertaken in order to evaluate semiquantitatively the nature and the distribution of epithelial mucins and the secretion of carcinoembryonic antigen (CEA). Ten HPC had a peculiar morphologic pattern (four with regenerative dysplasia and six with adenomatous foci). CEA secretion was always increased (37 per cent of cases) or highly increased (63 per cent of cases) with respect to the normal colonic mucosa. The nature and distribution of the secreted acid mucins were modified: sulfomucin was equal (25 per cent of cases) or higher (75 per cent of cases) than that in normal rectal or sigmoid colonic mucosae; sialomucin was strongly decreased in 91 per cent of cases. Some of these functional changes (CEA) are also observed in neoplastic lesions. These findings are not in accord with the hypothesis that hyperplastic polyp is a simple hyperplasia of the mucosal epithelium and suggest a disorder in cellular differentiation, particularly for the larger polyps.