Morphologic patterns observed in prostate biopsy cases with discrepant grade group and molecular risk classification

• Published in: The Prostate 2024-08, Vol.84 (11), p.1076-1085
• Main Authors: Greenland, Nancy Y., Cooperberg, Matthew R., Carroll, Peter R., Cowan, Janet E., Simko, Jeffry P., Stohr, Bradley A., Chan, Emily
• Format: Article
• Language: English
• Subjects: Aged; Biomarkers, Tumor - genetics; Biopsy; Cancer; Carcinoma; Collagen; Decipher; Decision making; Electronic medical records; Humans; Male; Metastases; Middle Aged; molecular risk classifier; Mucin; Neoplasm Grading; Prostate; Prostate - pathology; Prostate cancer; Prostatectomy; Prostatic Neoplasms - genetics; Prostatic Neoplasms - pathology; Risk Assessment; Rupture; Vacuoles
• ISSN: 0270-4137; 1097-0045; 1097-0045
• DOI: 10.1002/pros.24725

Background Molecular‐based risk classifier tests are increasingly being utilized by urologists and radiation oncologists to guide clinical decision making. The Decipher prostate biopsy test is a 22‐gene RNA biomarker assay designed to predict likelihood of high‐grade disease at radical prostatectomy and risk of metastasis and mortality. The test provides a risk category of low, intermediate, or high. We investigated histologic features of biopsies in which the Grade Group (GG) and Decipher risk category (molecular risk) were discrepant. Methods Our institutional urologic outcomes database was searched for men who underwent prostate biopsies with subsequent Decipher testing from 2016 to 2020. We defined discrepant GG and molecular risk as either GG1‐2 with high Decipher risk category or GG ≥ 3 with low Decipher risk category. The biopsy slide on which Decipher testing was performed was re‐reviewed for GG and various histologic features, including % Gleason pattern 4, types of Gleason pattern 4 and 5, other “high risk” features (e.g., complex papillary, ductal carcinoma, intraductal carcinoma [IDC]), and other unusual and often “difficult to grade” patterns (e.g., atrophic carcinoma, mucin rupture, pseudohyperplastic carcinoma, collagenous fibroplasia, foamy gland carcinoma, carcinoma with basal cell marker expression, carcinoma with prominent vacuoles, and stromal reaction). Follow‐up data was also obtained from the electronic medical record. Results Of 178 men who underwent prostate biopsies and had Decipher testing performed, 41 (23%) had discrepant GG and molecular risk. Slides were available for review for 33/41 (80%). Of these 33 patients, 23 (70%) had GG1‐2 (GG1 n = 5, GG2 n = 18) with high Decipher risk, and 10 (30%) had GG ≥ 3 with low Decipher risk. Of the 5 GG1 cases, one case was considered GG2 on re‐review; no other high risk features were identified but each case showed at least one of the following “difficult to grade” patterns: 3 atrophic carcinoma, 1 collagenous fibroplasia, 1 carcinoma with mucin rupture, and 1 carcinoma with basal cell marker expression. Of the 18 GG2 high Decipher risk cases, 2 showed GG3 on re‐review, 5 showed large cribriform and/or other high risk features, and 10 showed a “difficult to grade” pattern. Of the 10 GG ≥ 3 low Decipher risk cases, 5 had known high risk features including 2 with large cribriform, 1 with IDC, and 1 with Gleason pattern 5. Conclusions In GG1‐2 high Decipher risk cases, difficult to grade patt