During the last few years accumulating evidence has established that both cribriform pattern prostate cancer and intraductal carcinoma represent histologies with adverse prognostic impact, independent of Gleason grading. Their presence in biopsies and radical prostatectomy specimens is associated with increased risk of extraprostatic extension, biochemical recurrence after treatment, and metastatic disease. Therefore ISUP 2019 now recommends mandatory reporting of cribriform pattern and intraductal carcinoma. For practical reasons, the 2014 ISUP recommendation against grading of intraductal carcinoma in the context of an invasive carcinoma has been revisited. Thus, for instance, intraductal carcinoma with comedo necrosis will be graded as Gleason grade 5 and incorporated in the Gleason score of the specimen.
Histologically, prostate cancers can be very heterogeneous and one tumor may harbor three different Gleason patterns, ranging from Gleason grade 3-5, but the Gleason score includes only two grades. Literature shows the unfavorable prognostic impact of tertiary grade 5 at prostatectomy. The rule is now that a tertiary grade 5 will be incorporated in the Gleason score if comprising more than 5% of the carcinoma. If less than 5%, its presence will be commented upon. If a carcinoma in a prostatectomy largely consists of Gleason pattern 3 with less than 5% Gleason grade 4 pattern (minor pattern), biochemical recurrence risk might be slightly elevated, but this would not alter patient management. In this situation, the reported ISUP grade would remain 1 with a comment on the presence of a minor grade 4 component. This simplification of minor/tertiary grade reporting for both minor/tertiary Gleason pattern 4 and 5 may also help reduce upgrading at the time of prostatectomy and improve the accuracy of prostate biopsy grading.
MRI-targeted biopsies generally comprise multiple cores per target and the ISUP now recommends providing an aggregate ISUP grade (and percentage high grade) rather than the ISUP grade of the worse core, separately reporting ISUP grade and percentage high grade for each MRI suspicious lesion. It remains optional to provide a global ISUP grade of systematic biopsies. It is not unusual that a PIRADS 4 or 5 lesion does not yield a prostate cancer at targeted biopsy. The false positivity may be caused by specific benign histology such as fibromuscular hyperplasia, benign prostatic hyperplasia (BPH) nodule, or granulomatous inflammation. The ISUP 2019 now recommends reporting specific benign histologies if present in MRI targeted biopsies. It was felt that this might reduce patients’ anxiety by providing an explanation for a false positive MRI result.
Written by: Theodorus H. Van der Kwast, MD1, Geert J.L.H. Van Leenders, MD2, and Kenneth A. Iczkowski, MD3
- Laboratory Medicine Program, Princess Margaret Cancer Center, Toronto, Canada
- Department of Pathology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Pathology, Medical College of Wisconsin, Milwaukee, USA