Electron microscopy of polyps of the colon. I. Comparative study of the epithelial cells of adenomatous and adenopapillary polyps.

By comparing the electron-microscopic pictures of adenomatous and adenopapillary polyps, the ultrastructural characteristics of premalignant epithelial dysplasia were studied. In highly differentiated adenomatous polyps, the ratio and the electron-microscopic appearance of absorptive and goblet cells did not differ from the epithelial cells of the normal mucosa of the colon. In the dysplastic regions of adenopapillary polyps, the intensive proliferation in several layers of undifferentiated epithelial cells, and the maturation disorder of absorptive and goblet cells, were observed. Severe changes occurred on the cell membrane as well as atypical vacuoles and dense bodies in the apical regions of the cell membrane. Several inclusion bodies of Leuchtenberger were observed, these being considered an important characteristic of malignant transformation.