title: Interobserver reproducibility of percent Gleason grade 4/5 in prostate biopsies.
abstract: OBJECTIVE
  Percent Gleason grade 4/5 (GG4/5) has been proposed as a predictor of prognosis in prostate cancer and it has been shown to add prognostic information to that given by Gleason score (GS). We recently noted that the interobserver reproducibility of percent GG4/5 in total prostatectomy specimens is at least as good as that of the GS. However, to our knowledge the reproducibility of percent GG4/5 in needle biopsies has not yet been investigated.
  
  
  METHODS
  A consecutive series of needle biopsies from 69 men with prostate cancer was reviewed. Biopsies were taken according to a standardized octant protocol. All 279 slides containing cancer were circulated among 4 genitourinary pathologists, who assessed GS and percent GG4/5. Results were compared pairwise and weighted kappa was calculated.
  
  
  RESULTS
  The 4 observers had a mean weighted kappa for GS and percent GG4/5 of 0.48 to 0.55 (overall mean 0.51) and 0.52 to 0.68 (overall mean 0.60), respectively. There was less disagreement in percent GG4/5 when a single biopsy was positive for cancer than when 6 or more biopsies were positive. The number of positive biopsies showed a stronger correlation with a discrepancy in percent GG4/5 than cancer length. Disagreement was worse when cribriform or fusion patterns were present.
  
  
  CONCLUSIONS
  Interobserver reproducibility of percent GG4/5 on prostate biopsies is at least as good as that of GS. Hence, concern about interobserver variability should not deter pathologists from using percent GG4/5. Grading appears to be most difficult when cancer is present in multiple biopsies or it contains cribriform or fusion patterns.
authors.affiliation: Department of Pathology, Karolinska Hospital, Stockholm, Sweden.
authors.forename: Axel
authors.initials: A
authors.lastname: Glaessgen
authors.forename: Hans
authors.initials: H
authors.lastname: Hamberg
authors.forename: Carl-Gustaf
authors.initials: CG
authors.lastname: Pihl
authors.forename: Birgitta
authors.initials: B
authors.lastname: Sundelin
authors.forename: Bo
authors.initials: B
authors.lastname: Nilsson
authors.forename: Lars
authors.initials: L
authors.lastname: Egevad
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001707:Biopsy, Needle / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results