Grading of Prostate Cancer: The Impact of Including Intraductal Carcinoma on the Overall Grade Group Assigned in Diagnostic Biopsies.

The Gleason score/Grade Group (GS/GrG) is a key parameter for clinical decision-making in prostate cancer. The WHO currently recommend that intraductal carcinoma (IDCP) should not be factored into the GrG, however, grading of IDCP is controversial with variability among genitourinary pathologists. This study evaluated the impact of grading the IDCP component on the final GrG in prostate biopsies (PBx).

The study included 123 PBx with invasive carcinoma GrG1-GrG4 and IDCP. All cases were graded by a genitourinary pathologist using two different methods: i) grading of invasive carcinoma only ii) grading of both invasive carcinoma and IDCP. The overall GrG excluding the IDCP component was GrG1 in 3% (n=4), GrG2 in 36% (n=44), GrG3 in 53% (n=65) and GrG4 in 8% (n=10). When the IDCP component was included in grading, the overall GrG changed in 28 cases (23%). The GrG increased by 1 grade in 15/28 cases (54%), and by ≥2 grades in 13/28 cases (46%). Upgrading was due to comedonecrosis (39%,11/28), solid growth (4%,1/28) or increased proportion of Gleason pattern 4 (57%,16/28).

While the GrG was unchanged in the majority of cases, grading of IDCP altered the final GrG in a significant minority of biopsies in this series and often by more than one grade, which may have important implications for risk categorization of individual patients. These findings highlight the need for consensus on grading of IDCP in routine practice and the optimal method of incorporating IDCP into clinical risk models for patient management.

Histopathology. 2020 May 01 [Epub ahead of print]

Daphne Chen-Maxwell, Susan Prendeville

Department of Histopathology, Cork University Hospital, Cork, Ireland.