[Reproducibility of malignancy grading in prostatic cancers using the Gleason-Böckling system]

Histologic slides from 50 cases of prostatic adenocarcinoma were evaluated by 5 pathologists, in order to test the reproducibility of grading in two systems. Twenty-five needle core biopsies and 25 surgical (adenomectomy) specimens were graded in two sessions, according to the histomorphologic criteria of Gleason and Böcking. The results were analyzed by the kappa statistics. In surgical specimens, there were no significant differences in the interobserver reproducibility of microscopically assessed categories. In needle biopsies, however, Gleason's primary pattern (62%, kappa = 0.42), and Böcking's histological pattern (63%, kappa = 0.37) showed the highest level of agreement. Among the computed (derivated) classification terms, those consisting of only 3 groups (Gleason grouping, kappa = 0.39; Böcking grade, kappa = 0.39) proved to be better reproducible than the corresponding score values (p < 0.05). When compressing both systems into two grades (high and "non-high"), reproducibility was improved (kappa = 0.52). For a substantial improvement of grading results, more accurate grade definitions, continuing training and regular consultation of pathologists are necessary. Based on the results obtained by intraobserver analysis we conclude that kappa statistics is of limited value when analyzing the role of individual experience at grading reproducibility.