An ultrastructural and histochemical study of the mucous membrane adjacent to and remote from carcinoma of the colon.

The material was taken from surgical specimens of large intestine resected for carcinoma. A parallel study by electron microscopy and mucin histochemistry was made on fragments from "transitional" (TR) mucosa (adjacent to carcinoma) and "normal" (N) mucosa (remote from the tumor). These were compared with similar studies on the mucosa from control individuals. Histochemically, the "TR" mucosa shows an increase in sialomucins as compared with the "N" and control mucosae, where sulphomucins normally predominate. At the ultrastructural level, the "TR" mucosa is characterized by the following changes which may precede the histochemical variations: A) alteration in the relative proportions of the different cell types, along the crypt, with a persistence of immature and intermediate cells at higher levels of the crypt than in the control. Mature absorptive cells are fewer and bear an inverse relationship to intermediate cells. Goblet cells are increased in number and size. B) Appearance of electron-dense bodies 0.15-0.3mum in in diameter and membrane limited. C) An elaborated and enlarged Golgi zone showing increased secretory activity. It is suggested that mucin and ultrastructural changes described in the "TR" zone may indicate a failure in the normal process of cell differentiation along the crypt. Previous work7,8 further suggests that the mucin changes may be primary, reflecting a cellular response to unknown stimuli (i.e., carcinogens) rather than a local secondary effect of tumor growth. As for the ultrastructural features in the "TR" mucosa, the secondary effect cannot be excluded at the present.