E. David Crawford, MD asked expert Francisco G. La Rosa, MD, FACS about reporting Gleason grades.
Question by E. David Crawford, MD: Dr. La Rosa, there seems to be some variation on how prostate biopsies are reported. My recollection of the Gleason system is that the most predominant pattern is reported. Please explain how a biopsy may be reported as a Gleason eight whereas the tumor may be a Gleason seven (i.e. 3+4).
Answer by Francisco G. La Rosa: This apparent discrepancy may be due to two different scenarios: (1) Since prostate cancers are usually multifocal, TRUS biopsies may be targeting different tumors, one may be 4 + 4 = 8 and another nearby tumor may be a mixture of Gleason grades 3 and 4. The only way to determine that these are different tumors is with examination of a whole mount prostatectomy section. (2) If the tumor is unifocal and TRUS biopsies show differences in Gleason grades, this is due to the heterogeneity of prostate tumors, which usually show areas with only one Gleason grade (i.e. Gleason 4 + 4 = 8) and other areas with a mixture of other grades (i.e. 4+3 or 3+4). This is illustrated in the figure below, which shows one section of a whole mount prostatectomy specimen, in which Gleason grades of the tumor have been outlined with green dots for Gleason grade 3 and purple for Gleason grade 4. Depending on the area of the tumor targeted by the needle biopsy, we may obtain different Gleason grade combinations of a Gleason 3 + 4 = 7 tumor.
Prostatic adenocarcinoma Gleason grade 3 + 4 = 7 (Gleason grade 4 is ~20%)
Depending on the targeted area, TRUS biopsies will sample different mixed combinations
of Gleason grades. The final Gleason grade will be determined on the whole mount