(UroToday.com) Dr. Geert Van Leenders of the Netherlands provides the Pathology perspective on quantifying Gleason pattern 4 for active surveillance (AS). First, he highlights the fact that Gleason pattern for disease is a heterogeneous subset. Historically Gleason pattern 4 was a single entity – but recent research has demonstrated that Gleason pattern has multiple histologic subsets. These include fused glands, ill-formed glands, glomeruloid histology, and importantly intraductal (IDC) and cribriform patterns. We now know that separating out IDC/cribriform pattern 4 is critical and has oncologic implications. As seen in the K-M curve below, when GG2 disease is stratified by the presence/absence of IDC/cribriform pattern, men with GG2 without these features have similar outcomes to men with GG1 disease. But, men with those features have much worse metastases-free survival.