Reliability of Gleason grading system in comparing prostate biopsies with total prostatectomy specimens.

Prostate biopsy and total prostatectomy specimens from 31 patients with adenocarcinoma of the prostate were compared using the Gleason histopathologic grading system. The overall accuracy when grouping the scores into three categories (2-4, 5-7, and 8-10) was 81 per cent. The incidence of critical undergrading was 6 per cent while the incidence of critical overgrading was 13 per cent. Eighty-seven per cent of the biopsy scores were plus or minus 1 Gleason unit of the prostatectomy scores. Intraobserver variation was less than 1 Gleason unit. The mean absolute difference between the biopsy and the total prostatectomy specimen was 0.77 Gleason units. The Gleason category score of the total prostate specimen can be predicted from the biopsy tissue with reasonably good accuracy. The limitation of this grading system in predicting the presence or absence of pelvic node involvement is discussed.