Intraductal carcinoma (IDC) is an adverse histopathological parameter for prostate cancer outcome, but not incorporated in current tumour grading. To account for its dismal prognosis and omit basal cell immunohistochemistry, it has been proposed to grade IDC based on its underlying architectural pattern. Our objective was to determine the impact of IDC grade assignment on prostate cancer biopsy and radical prostatectomy tumour grading.
A cohort of 1,031 prostate cancer biopsies and 835 radical prostatectomies was assigned a Grade Group according to the 2014 International Society of Urological Pathology (ISUP) guidelines, not incorporating IDC in grading. Tumour grading was compared with a Grade Group in which IDC was graded based on its underlying architecture. Out of 1,031 biopsies, 139 (13.5%) had IDC. Grade assignment to IDC led to a Grade Group change in 17 (1.6%) cases: 4/486 (0.8%) Grade Group 1 were reclassified as Grade Group 2, 9/375 (2.4%) Grade Group 2 as 3, and 4/58 (6.9%) Grade Group 4 as 5. IDC was observed in 213/835 (25.5%) radical prostatectomies and its grading led to a shift in tumour grade in 5/835 (0.6%) men, with upgrading in 2/207 (1.0%) men with Grade Group 1, 2/420 (0.5%) with Grade Group 2, and 1/50 (2%) with Grade Group 4 cancer.
IDC grade assignment led to a Grade Group change in 1.6% of prostate biopsy and 0.6% of radical prostatectomy specimens. Although inclusion/exclusion of IDC from the Grade Group might affect decision-making in individual patients, it has minimal impact on overall prostate cancer management.
Histopathology. 2020 Jun 15 [Epub ahead of print]
L Lucia Rijstenberg, Tim Hansum, Eva Hollemans, Charlotte F Kweldam, Intan P Kümmerlin, Chris H Bangma, Theodorus H van der Kwast, Monique J Roobol, Geert J L H van Leenders
Department of Pathology, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands., Department of Urology, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands., Laboratory Medicine Program, University Health Network, Toronto, Canada.