Grading The Cancer Healthy prostate cells are uniform in size and shape, neatly arranged in the patterns of a normal gland. As cancer grows, they lose their healthy look. They change from normal, well-differentiated tissues to more disorganized, poorly differentiated tissue. Eventually, a tumor develops. If your biopsy shows the presence of prostate cancer, the pathologist assigns each tissue sample a grade , indicating how far the cells have traveled along the path from normal to abnormal.
Tumor grade is useful as a predictor of outcome.
The chances of developing metastatic prostate cancer followed a similar pattern. Ten years after surgery, metastases had been diagnosed in 13 percent of the men with well-differentiated tumors, but in 32 percent of those with cancers that were moderately differentiated and 48 percent of those whose cancers were poorly differentiated. The Gleason grading system assigns a grade to each of the two largest areas of cancer in the tissue samples. Grades range from 1 to 5, with 1 being the least aggressive and 5 the most aggressive. Grade 3 tumors, for example, seldom have metastases, but metastases are common with grade 4 or grade 5.