[780] Gleason Pattern 5 Is Frequently Underdiagnosed on Prostate Needle Core Biopsy

Turki Al-Hussain, Michael S Nagar, Jonathan I Epstein. The Johns Hopkins Hospital, Baltimore

Background: The current study assesses underdiagnosing Gleason pattern 5 on biopsy and discuss the potential consequences for patient management.
Design: We retrieved 300 consecutive prostate biopsy cases from our consultation files from 2009-2010 in which we identified Gleason pattern 5. All cases were diagnosed by one expert GU pathologist, and were sent in as a final diagnosis, where the outside pathologist was not requesting consultation as a result of difficulty with the diagnosis. Cases typically were sent for consultation at the request of the patient or the outside treating physician.
Results: Table compares Gleason grades rendered upon expert review (EXP) compared to those at the outside institutions (OS).

	OS 3+3=6	OS3+4=7	OS4+3=7	OS3+5=8	OS5+3=8	OS4+4=8
EXP3+5=8	2 (6.5%)	15 (48.4%)	1 (3.2%)	10 (32.2%)	0	1 (3.2%)
EXP5+3=8	0	0	4 (44.5%)	0	3 (33.3%	1 (11.1%)
EXP4+5=9	1 (0.8%)	11 (8.8%)	21 (16.8%)	3 (2.4%)	1 (0.8%)	51 (40.8%)
EXP5+4=9	0	1 (1.4%)	5 (7.0%)	2 (2.8%)	1 (1.4%)	24 (33.3%)
EXP5+5=10	0	0	0	1 (1.6%)	1 (1.6%)	8 (12.7%)

	OS4+5=9	OS5+4=9	OS5+5=10	Total
EXP3+5=8	2 (6.5%)	0	0	31 (100%)
EXP5+3=8	1 (11.1%)	0	0	9 (100%)
EXP4+5=9	33 (26.4%)	4 (3.2%)	0	125 (100%)
EXP5+4=9	23 (31.9%)	15 (20.8%)	1 (1.4%)	72 (100%)
EXP5+5=10	19 (30.1%)	8 (12.7%)	26 (41.3%)	63 (100%)

Of the 300 cases, 203 cases (68%) were under-graded, 93 cases (31%) were graded the same, and 4 cases (1%) were overgraded relative to the grade assigned by the expert pathologist. In 146 (48.7%) of the cases, Gleason Pattern 5 was not identified by the outside pathologists. Of the 146 cases, the outside Gleason score was ≤7 in 61 (20.3%) and 4+4=8 in 85 (28.4%) of the cases. Even when the tumor was diagnosed at our institution as Gleason score 5+5=10), only 26 (41.3%) were diagnosed as the same by the outside pathologists.
Conclusions: Gleason pattern 5 is commonly underdiagnosed by outside pathologists compared to an expert GU pathologist. One explanation is a hesitancy of pathologists to render the worst grade pattern possible and its adverse implications on prognosis and treatment. Another explanation is that some cases may have consisted of mostly pattern 4, less pattern 3 (or vice versa), and tertiary pattern 5. According to the ISUP modified grade, Gleason score on biopsy is derived by adding the most prevalent and highest grade patterns as opposed to the most and 2^nd most common patterns. Not using the ISUP modified grading system could have accounted for at most 36/146 (24.7%) of the cases where Gleason pattern 5 was not recorded by the outside pathologists. Recognition of undergrading pattern 5 is the first step to improving its grading in the future by diverse educational means.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 2:30 PM

Platform Session: Section A, Monday Afternoon