Gleason Grading of Prostatic Carcinoma

Prognosis

The Gleason grading system is one of the most powerful prognostic indications for prostatic carcinoma. Gleason score correlates with all of the important pathologic parameters in radical prostatectomy specimens, with outcome after radical prostatectomy or radiotherapy, and with prognosis in patients who elect to have treatment deferred. Differentiating Gleason score 6 from 7 is particularly important because a major shift, in terms of likelihood of having adverse findings in the prostatectomy specimen, or with failure following prostatectomy or radiotherapy, occurs between these two scores. In addition to behaving significantly worse than Gleason score 5-6 tumors, Gleason score 7 tumors behave significantly better than Gleason score 8-10 tumors. The following combination of Gleason scores results in groups with similar prognosis: Gleason score 2-4 (well-differentiated), and Gleason score 8-10 (poorly differentiated). We have already noted that Gleason score 7 is commonly undergraded (see Problem Areas). The importance of learning to accurately diagnose Gleason score 7 is magnified by the fact that it is the only one of the four prognostic groups consisting of only one Gleason score.

A number of nomograms have been developed to predict pathologic stage (including extra-prostatic extension and lymph node metastasis), post-radical prostatectomy progression and post-radiotherapy failure. Gleason grading is an integral part of these nomograms and, as such, accurate Gleason grading is essential.