Computer-assisted 3D mapping and morphometry of dysplastic zones in endoscopically resected colonic adenomas

Three-dimensional (3D) reconstruction and morphometry of resected colonic adenomas were undertaken to extend current knowledge of clinically significant features such as the frequency of occurrence of cancer, and the size and spatial distribution of dysplastic zones in these tumours. Fifty endoscopically resected colonic adenomas were serially sectioned at intervals of 0.2 mm and the sectional images were loaded into a computer system in order to visualize the spatial distribution of dysplastic zones. These were graded into five groups according to the criteria of Morson and Dawson: normal mucosa, mild dysplasia, moderate dysplasia, severe dysplasia, and cancer. The way in which zones of different grades are distributed in a polyp was visualized in a computer display and the volume of each dysplastic zone was estimated by the Cavalieri principle. In five polyps, adenocarcinoma was found growing in an adenoma. In all of these, the cancer was surrounded by less dysplastic zones, in the form of 'cancer in adenoma'. In pedunculated polyps, submucosal invasion could occur even if the volume percent of severe dysplasia was less than 10%. In such a case, multiple biopsy specimens are advisable. Semipedunculated polyps smaller than 200 mm(3) can also harbour submucosal invasion. In this study it was found that if the adenomas had been examined by only a single section, as many as one in five of the cases in which submucosal invasion had already developed would have escaped microscopic confirmation. To prevent such diagnostic failure, it is advisable to add a few deeper sections. Thus, 3D reconstruction and morphometry have been helpful in establishing a better standard for the diagnostic histopathology of colonic tumours.