Proliferation index of different Gleason pattern 4 histomorphologies and associated pattern 3 adenocarcinoma of the prostate

Gleason grade is one of the most powerful prognostic indicators for adenocarcinoma of the prostate. A higher proliferation index of prostatic adenocarcinoma has been demonstrated in numerous studies to be significantly associated with more aggressive behavior. To date, the proliferation index of the different Gleason pattern 4 histomorphologies, including cribriform, fused glands, and poorly formed glands, has not been determined. The aim of this investigation was to quantitate and compare the proliferation index, as assessed by Ki67 labeling index, of different Gleason pattern 4 histomorphologies. We also analyzed the Ki67 labeling index of Gleason pattern 3 adenocarcinoma associated with and without cribriform adenocarcinoma. Among Gleason pattern 4 morphologies, cribriform adenocarcinoma exhibited a higher mean proliferation index at 5.3% compared to fused gland adenocarcinoma at 3.9% (P = .03) and poorly formed glands at 3.6% (P < .01). The mean Ki67 labeling index for Gleason pattern 3 associated with cribriform adenocarcinoma was higher at 4.1% compared to pure Gleason pattern 3 at 2.2% (P < .01) and Gleason pattern 3 associated with non-cribriform pattern 4 adenocarcinoma at 2.9% (P = .02). This higher proliferation index of Gleason pattern 3 adenocarcinoma associated with cribriform pattern 4 adenocarcinoma indicates that not all Gleason pattern 3 cells are identical and that cribriform adenocarcinoma may influence or be related to associated Gleason pattern 3. Gleason pattern 4 adenocarcinoma of the prostate with cribriform growth has a higher proliferation index than other grade 4 histomorphologies, consistent with the more clinically aggressive nature of cribriform adenocarcinoma of the prostate.