Mucin secretion and morphological changes of the mucosa in non-neoplastic diseases of the colon.

Changes in mucin secretion and increase in height of the colonic mucosa adjacent to colorectal carcinoma (transitional mucosa) have been considered pre-malignant. In this study similar changes (both morphological and histochemical) have been found in some cases of ulcerative colitis and ischaemic colitis, as well as in juvenile, inflammatory and hyperplastic (metaplastic) polyps. 'Transitional' patterns of mucin secretion also occur in some other cases of ulcerative colitis, colostomies and Crohn's disease of the colon in which the mucosa has a normal height, suggesting the changes in mucin secretion are independent of mucosal morphology. In all these pathological conditions, hyperplastic (metaplastic) mucosa also coexisted. These findings seem to suggest that: (1) 'transitional' changes more likely represent a secondary regenerative phenomenon rather than a premalignant one; (2) the pattern of mucin secretion is not selective enough to serve as a premalignant marker; therefore is not a valid prognostic indicator in colonic biopsies; (3) hyperplastic (metaplastic) changes might derive from 'transitional' mucosa as a result of a more mature phase of this exaggerated regenerative phenomenon. However, in some patients longstanding 'transitional' mucosa may lead to dysplasia under the influence of environmental and genetic factors.