Interobserver Reproducibility of Percent Gleason Pattern 4 in Prostatic Adenocarcinoma on Prostate Biopsies

Abstract

In the WHO Classification of Tumours of the Urinary System and Male Genital Organs published in 2016, it was officially recommended that the percent of Gleason pattern 4 (GP4) be reported on pathology reports to better reflect the extent in Gleason score 7 tumors. In this study we assessed the reproducibility of reporting GP4 on prostate biopsies. We analyzed prospectively 422 cores containing GP4 from our consult cases over a period of 2.5 months. The percent pattern 4 was assigned to all the cases in 10% increments from 0% to 100% (with the addition of 5%) by 1 of 4 fellows in urological pathology and by the expert urological pathologist. Out of 422 cores, 32% were an exact match and 75% were within ±10% (weighted κ [κW] value 0.67). Cases were further stratified on the basis of (1) scattered versus clustered GP4 in the background of Gleason pattern 3, (2) continuous versus discontinuous tumor involvement, (3) cribriform/glomeruloid pattern only versus poorly formed/fused pattern versus mixed cribriform and poorly formed/fused pattern, and (4) total tumor involvement of the core (≤10% vs. >10% of the core). No significant differences were observed in the first 3 variables. However, in cases with ≤10% involvement of the core, 61% were within ±10% (κW=0.50) compared with cases with >10% involvement of the core, in which 78% were within ±10% (κW=0.70). In summary, we showed that assessment of percent GP4 was relatively reproducible, with substantial agreement within ±10% in cases. However, with <10% involvement of the core, it was more difficult to assess in smaller foci, with only moderate agreement. Given that in a small focus only a few glands of a given pattern can markedly affect the percent GP4, consideration should be given to not recording percent GP4 in small foci of Gleason score 7 tumors on needle biopsy.

Computer aided detection in prostate cancer diagnostics: A promising alternative to biopsy? A retrospective study from 104 lesions with histological ground truth

“…Nonetheless, MAI did not significantly correlate with the pathological outcome, which is the Gleason score in our database. Inter-observer differences in Gleason grading between the training and the testing database could already contribute to this discrepancy, albeit minimally, as previous studies have shown negligible inter-observer variation mostly at the upper and lower limit, namely 4 and 8–10 of the Gleason scale [43,44]. Another possible variability factor may rely on the classifier´s training on whole slide pathology specimens, whereas the grading process in the current study was based on needle biopsies [45,46].…”

Prostate cancer grading: a decade after the 2005 modified system

“…Assessing the percent Gleason pattern 4 is relatively reproducible, with substantial agreement within ± 10% in cases. 48 Cases where patterns 3 and 4 are intermingled are more difficult to assess for percent pattern 4. 49 We have shown that there is only moderate interobserver agreement for assessing the percent pattern 4 with o 10% involvement of the core by cancer, as a few glands of a given pattern can markedly affect the percent of Gleason pattern 4.…”

“…49 We have shown that there is only moderate interobserver agreement for assessing the percent pattern 4 with o 10% involvement of the core by cancer, as a few glands of a given pattern can markedly affect the percent of Gleason pattern 4. 48 As a result, some experts do not record percent pattern 4 in small foci of Gleason score 7 tumors on needle biopsy, although other experts routinely reports percent pattern 4 for call cases of Gleason score regardless of tumor extent.…”

Grading of prostate cancer: a work in progress

“…One study reported that interobserver reproducibility of percent Gleason grades 4 or 5 on prostate biopsies is at least as good as that of Gleason score . A subsequent reproducibility study on percentage Gleason grade 4 in prostate biopsies revealed that when reported in 10% increments, 32% had an exact match between fellow and expert urological pathologist and 75% were within a 10% range with a good (weighted kappa of 0.67) agreement . The agreement for percentage Gleason pattern 4 decreased significantly only when carcinoma comprised 10% or less of the core.…”