Interobserver reproducibility of Gleason grading of prostatic carcinoma: Urologic pathologists

Gleason grading is now the most widely used grading system for prostatic ca rcinoma in the United States. However, there are only a few studies of the interobserver reproducibility of this system, and no extensive study of int erobserver reproducibility among a large number of experienced urologic pat hologists exists. Forty-six needle biopsies containing prostatic carcinoma were assigned Gleason scores by 10 urologic pathologists. The overall weigh ted kappa coefficient KW for Gleason score for each of the urologic patholo gists compared with each of the remaining urologic pathologists ranged from 0.56 to 0.70, all but one being at least 0.60 (substantial agreement). The overall kappa coefficient kappa for each pathologist compared with the oth ers for Gleason score groups 2-4, 5-6, 7, and 8-10 ranged from 0.47 to 0.64 (moderate-substantial agreement), only one less than 0.50. At least 70% of the urologic pathologists agreed on the Gleason grade group (2-4, 5-6, 7, 8-10) in 38 ("consensus" cases) of the 46 cases. The 8 "nonconsensus" cases included low-grade tumors, tumors with small cribriform proliferations, an d tumors whose histology was on the border between Gleason patterns. Intero bserver reproducibility of Gleason grading among urologic pathologists is i n an acceptable range. Copyright (C) 2001 by W.B. Saunders Company.