Conversely, the cells of Grade 3 or Grade 4 tumors are usually poorly differentiated or undifferentiated high-grade tumors, and are generally the most aggressive in behavior. Some cancers also have special grading systems. For example, pathologists use the Gleason system to describe the degree of differentiation of prostate cancer cells. The Gleason system uses scores ranging from Grade 2 to Grade 10. Lower Gleason scores describe well-differentiated, less aggressive tumors.
Higher scores describe poorly-differentiated, more aggressive tumors.
Patients should discuss questions about tumor grade and how it relates to their diagnosis and treatment with their doctor.