Tertiary Gleason pattern 5 on needle biopsy predicts greater tumour volume on radical prostatectomy

The modified Gleason system of 2005 recommends incorporating higher grade tertiary patterns on needle biopsy into final Gleason scores to better correlate with radical prostatectomy findings. However, limited literature exists on the validity of this practice and the significance of tertiary Gleason patterns in needle biopsy.

Over a 20 month period there were 25 cases of Gleason score 7 with tertiary pattern 5 on needle biopsy with follow-up radical prostatectomy reported at our institution. Pathological findings at radical prostatectomy from these cases were compared with those from patients with Gleason score 4 + 3 = 7 tumours (50 cases) and Gleason score 4 + 5 = 9 tumours (63 cases) on needle biopsy.

Comparison of Gleason score 4 + 3 = 7 with 4 + 3 = 7(+5) tumours on needle biopsy, showed a significant difference in tumour volume in the corresponding radical prostatectomy specimen (p = 0.02). Differences in patient age, serum prostate specific antigen levels at diagnosis, positive surgical margins, extraprostatic extension, seminal vesicle invasion and lymph node metastases were not statistically significant between the two patient groups or when Gleason score 4 + 3 = 7(+5) and Gleason score 9 tumours were compared.

Tertiary pattern 5 on needle biopsy predicts greater tumour volume. This suggests that for thin core biopsies, if tertiary pattern 5 is present this should be incorporated into the final Gleason score.