The 2019 International Society of Urological Pathology (ISUP) Consensus Conference on Grading of Prostatic Carcinoma

Abstract

Five years after the last prostatic carcinoma grading consensus conference of the International Society of Urological Pathology (ISUP), accrual of new data and modification of clinical practice require an update of current pathologic grading guidelines. This manuscript summarizes the proceedings of the ISUP consensus meeting for grading of prostatic carcinoma held in September 2019, in Nice, France. Topics brought to consensus included the following: (1) approaches to reporting of Gleason patterns 4 and 5 quantities, and minor/tertiary patterns, (2) an agreement to report the presence of invasive cribriform carcinoma, (3) an agreement to incorporate intraductal carcinoma into grading, and (4) individual versus aggregate grading of systematic and multiparametric magnetic resonance imaging-targeted biopsies. Finally, developments in the field of artificial intelligence in the grading of prostatic carcinoma and future research perspectives were discussed.

Intraductal carcinoma has a minimal impact on Grade Group assignment in prostate cancer biopsy and radical prostatectomy specimens

“…In the latest 2019 ISUP consensus meeting on prostate cancer grading in Nice, France, it was agreed that IDC associated with invasive carcinoma should be graded on the basis of its underlying architectural pattern as if it were invasive disease. 25 The most important reasons for this recommendation were: (i) that it accounts for the adverse clinicopathological features associated with IDC, which is particularly important for men with Grade Group 1 cancers with IDC, who are at risk for undertreatment of their disease; and (ii) the omission of significant numbers of immunohistochemical stains, including those for which interpretation is arbitrary. 26 Our finding that exclusion of IDC from prostate cancer grading is associated with a Grade Group change in <2% of cases is supportive of this practical 2019 ISUP recommendation.…”

“…Although Gleason pattern 4 quantification is recommended for all Gleason score 7 (Grade Groups 2 and 3) prostate cancers, it is not clear to what extent this estimate includes IDC. 8,25 Grading practices of including IDC in tumour volume assessment and possibly Gleason pattern 4 quantification, but not in tumour grading, seem contradictory. The 2019 ISUP recommendation on grading of IDC associated with invasive adenocarcinoma is helping to overcome these inconsistencies.…”

Prostate cancer growth patterns beyond the Gleason score: entering a new era of comprehensive tumour grading

“…22 These rare cases of isolated IDC should not be graded, but a comment should indicate their association with unsampled high-grade carcinoma. 1,3,22,23 The finding of isolated IDC on needle biopsy should lead to immediate re-biopsy, and some even advocate radical treatment in these cases. 22 The International Society of Urological Pathology (ISUP) recommended in 2014 and the World Health Organization (WHO) recommended in 2016 that the presence of IDC without invasive carcinoma should be specifically mentioned, but no recommendations were made for reporting of IDC admixed with invasive cancer.…”

“…At the most recent ISUP consensus meeting in Nice, France, 2019, it was agreed that both invasive cribriform carcinoma and IDC should be specifically reported. 23 The grading of IDC intermixed with invasive carcinoma has been controversial. Whereas the 2014 ISUP meeting did not make a recommendation on this issue, in 2016 the WHO stated that it should not be factored into grading.…”

“…25 As IDC is an adverse pathological parameter, and difficult or even impossible to distinguish from invasive carcinoma even with the use of basal cell immunohistochemistry, it was recommended at the latest 2019 ISUP consensus meeting that IDC intermixed with invasive carcinoma should be assigned a Gleason grade based on its underlying growth pattern, as if it were invasive carcinoma. 23 On the other hand, the Genitourinary Pathology Society (GUPS) recommends not factoring IDC into Gleason grading, and performing basal cell immunohistochemistry if classification as either invasive carcinoma or IDC would lead to a change in the final Gleason score. 26 Thus, a Gleason score 6 prostate cancer biopsy with a cribriform lesion is now classified as Grade Group 2 according to the 2019 ISUP recommendation, without immunohistochemistry; the GUPS recommends performing basal cell immunohistochemistry and grading the tumour as Grade Group 1 if basal cells are present and as Grade Group 2 if they are not.…”