Abstract
Although rare, there are cases within reported series of men with GS≤6 in radical prostatectomies that have pelvic lymph node (LN) metastases. However, there are no studies as to whether pelvic LN metastases occur in tumors GS≤6 using the International Society of Urological Pathology (ISUP) updated Gleason scoring system. We performed a search of the radical prostatectomy databases at 4 large academic centers for cases of GS≤6. Only prostatectomies submitted and embedded in entirety with pelvic lymph node dissections were included. A combined total of 14,123 cases were identified out of which 22 cases had a positive LN. Histopathology review of 19 cases (3 cases unavailable for review) showed higher grade than originally reported by the pathologists in all cases. Of the 17 pre-ISUP reviewed cases, 2 were upgraded to 4+3=7 with both cribriform and poorly formed glands. One case was upgraded to 4+3=7 with tertiary pattern five displaying cribriform glands, poorly formed glands, and cords of single cells. Eleven cases were upgraded to 3+4=7 with glomeruloid structures and small to large cribriform glands (1 of these also had ductal adenocarcinoma features). Two cases had tertiary pattern 4 with small cribriform glands. One case had a prominent colloid component that would currently be graded as 4+5=9 due to large cribriform glands and solid sheets of cells within mucin. Of the two post-ISUP cases, one demonstrated tertiary pattern 4 and the other showed Gleason score 3+4=7 with irregular cribriform glands. Under-grading primarily accounts for LN positivity with GS ≤6, which has decreased significantly since the adoption of the ISUP grading system in 2005. Out of over 14,000 totally embedded RPs from multiple institutions, there was not a single case of a GS≤6 tumor with LN metastases. In contrast to prevailing assumptions, Gleason score ≤6 tumors do not appear to metastasize to lymph nodes. Rather, Gleason patterns 4 or 5, as better defined by the current ISUP updated grading system, is required for metastatic disease.
