Solitary and synchronous adenomas of the colon and rectum: comparison of malignancy parameters.

The histological, mucin histochemical and immunohistochemical features were evaluated of 74 solitary and 73 synchronous colorectal adenomas which were endoscopically removed from 124 patients. Of the patients, 60% had a single adenoma, whereas 40% had at least two adenomas in their colorectum. Comparing the incidence of synchronous adenomas in both sexes revealed a statistically significant higher incidence (P less than 0.005) in males. The localization of the solitary and synchronous adenomas in the large bowel was similar. Moreover, parameters of malignant change within the adenomas (size, predominant type of mucosal growth and degree of dysplasia-with the exception of severe dysplasia) as well as signs of dedifferentiation (relative proportions of goblet and columnar cells) were also similar. Mucin staining intensities (periodic acid-Schiff, high iron diamine and alcian blue) and the immunoreactivity patterns of secretory component and carcinoembryonic antigen, both cytoplasmic and on the surface of the epithelial cells, were also identical in both groups of adenomas. Thus, neither the routine histological nor the mucin- and immunohistochemical features differed between the groups, except for severe dysplasia. It is concluded that there is no inherent difference in malignant potential between solitary and synchronous adenomas, with the possible exception of the degree of dysplasia.