p16 Expression in Prostate Cancer and Nonmalignant Lesions: Novel Findings and Review of the Literature

BACKGROUND:Prostatic specimens occasionally may contain proliferative foci of the small atypical acini that display some but not all features of prostate carcinoma. p504s is the only prostatic cancer (PC)-specific marker that, in combination with basal cell markers, help in the diagnosis of malignant lesions. Very little is known about the diagnostic importance of p16 in primary prostate carcinoma and nonmalignant elements.MATERIALS AND METHODS:We recruited 137 of routinely diagnostic prostatic specimens (between 2009 and 2013), which consisted of 21 prostatectomy, 15 transurethral prostatic resection, and 101 needle biopsy. We evaluated p16, in comparison with p504s, in prostatic carcinoma and benign glands. In this study, both nuclear and cytoplasmatic p16 expression were considered positive.RESULTS:We observed p16 expression in 86% of PC specimens and 16% of benign elements (P=0.001). Interestingly, p16 alone retained a high diagnostic potential in prostatectomy (95%) and in needle biopsy (84%), exhibiting a close association with PC. p504s had a high sensitivity (97%) and predictive negative value (98%) but a low specificity (71%) and predictive positive value (63%). In contrast, p16-positive expression showed a higher specificity (84%) and predictive positive value (74%) than p504s. Two prostatic carcinoma negative for p504s were positive for p16, whereas 7 cases negative for p16 were positive for p504s, and notably none was negative for both markers. In prostatectomy, p16 showed a higher diagnostic accuracy but not on transurethral prostatic resection. In needle biopsies, both markers were complementary, indicating that their combined detection may help in performing an accurate diagnosis.In conclusion, our data suggest that p16 expression is significantly enhanced in prostate carcinoma as compared with nonmalignant elements. Our results provide evidence that p16 and p504s together could improve the diagnosis of PC in prostatectomy and needle biopsies.