Comparative electron microscopic features of normal, hyperplastic, and adenomatous human colonic epithelium. Variations in cellular structure relative to the process of epithelial differentiation.

Abstract

Abstract Electron microscopic studies of the epithelium of normal human colonic mucosa, hyperplastic polyps, and adenomatous lesions confirm and extend our previous studies of these tissues. In this study the cytology of well defined examples of the three types of epithelium is compared at several crypt levels. The normal epithelium exhibits a regular pattern of differentiation as cells migrate from the base of the crypt to the free surface. Progressive maturation is seen from undifferentiated cells in the base of the crypt to intermediate and immature goblet and absorptive cells in the midcrypt and, finally, to fully mature and even senescent goblet and absorptive cells in the upper one-third of the crypt and at the free surface. The hyperplastic epithelium exhibits a similar progression, the primary difference being that most of the morphological features of maturing and mature cells are found either lower in the crypt or in exaggerated form at the same level of the crypt when compared with normal mucosa of the same colon. The adenomatous epithelium, however, rarely differentiates past the intermediate, partially differentiated cell stage, retaining both the morphological and replicative characteristics of this immature cell type.