Grading Prostate 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 uniform appearance. 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. The grade offers a good clue to your tumor's behavior: a tumor with a low grade is likely to be slow-growing, while one with a high grade is more likely to grow aggressively or already to have spread outside the prostate (metastasized). The most widely used grading method for prostate cancer is known as the Gleason grading system.

Tumor grade is useful as a predictor of outcome. In one analysis, 10 years after prostatectomy for localized cancer, prostate cancer had claimed the lives of 6 percent of the men whose cancers were well differentiated compared with 20 percent of those with moderately differentiated cancers and 23 percent of those with poorly differentiated cancers. The chances of developing metastatic prostate cancer followed a similar pattern. Ten years after surgery, metastasis had been diagnosed in 13 percent of the men with well differentiated tumors, 32 percent of those with cancers that were moderately differentiated and 48 percent of those whose cancers were poorly differentiated.

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