MALIGNANCY POTENTIAL OF COLORECTAL POLYPS - HISTOMORPHOMETRIC, HISTOCHEMICAL AND IMMUNOHISTOCHEMICAL INVESTIGATIONS ON THE DYSPLASIA-CARCINOMA-SEQUENCE

Colorectal polyps are usually diagnosed endoscopically and are simulta neously removed. Since adenomatous polyps tend to become malignant, th ese deserve special attention. In order to prevent carcinomas arising from pre existing adenomas, a precise analysis of the lesions in the m ucous membrane of the polyps with regard to their malignancy potential is very important. Morphometric methods and determination of prolifer ation kinetics enable the dignity of a neoplasia to be assessed. Spora dic colorectal polyps were examined to what extent the morphometric an alysis of nuclear area, the silver staining of nucleolar organizer reg ions (AgNORs) and the immunhistochemical staining of the Ki67 antigen permit further differentiation of the growth pattern of the tumor. Tis sue from 50 hyperplastic polyps, 50 tubular and 50 tubulovillous adeno mas was endoscopically removed and investigated, whereas pure villous adenomas were not examined due to their relative infrequency. These ti ssues were compared with biopsies of normal colonic mucosa and also wi th invasive adenocarcinomas. The Ki67 score shows that the proliferati ve activity is not significantly different between normal colonic muco sa and hyperplastic polyps, however there is a noticable difference be tween the proliferation of the former types and colorectal neoplasias. The staining of the NORs does not reveal differences between the vari ous grades of dysplasia in tile adenomas, and therefore proves to be i nadequate for differentiation, whereas morphometric and immunhistochem ical measurements reveal appreciable selectivity, No correlation is ob served between the parameters from the morphometric, histochemical and immunhistochemical analysis, Using the methods mentioned above the dy splasia-carcinoma-sequence can be clearly differentiated, however the validity of the different measurements is very variable. The histomorp hometric analysis of the nuclear area, and particulary the staining of the Ki67 antigen seem to present suitable criteria for the differenti ation of harmless and potentially serious lesions of the colorectum.