@jeffmarc Gleason grade 1 is from the original system—it describes cancer cells that look almost exactly like normal prostate cells. In practice, pathologists almost never assign it anymore; they rarely use grades 1 or 2 at all.

Grade Group 1 is from the modern system introduced in 2014. It means the lowest-risk category of prostate cancer, corresponding to a Gleason score of 6 (3+3). These are slow-growing, well-formed glands that are much less aggressive.

In short: Gleason grade 1 is an outdated, rarely used microscopic pattern, while Grade Group 1 is the current clinical label for the least concerning prostate cancers—often managed with monitoring rather than treatment. Your report will likely show Grade Group 1, not Gleason grade 1.