MUC1 Expression in Incidental Prostate Cancer Predicts Staging and Grading on the Subsequent Radical Prostatectomy

The behavior of Incidental prostate cancer (IPC) cannot be reliably predicted by means of conventional histomorphology. MUC1 (episialin) expression has been linked to poor outcome in peripheral prostate cancer (PC). We aimed to determine the so far neglected prognostic role of MUC1 expression in IPC which most commonly represents transition zone cancer. Using Tissue microarray (TMA), we assessed the association between MUC1 expression recorded in transurethral resection specimens of the prostate (TURP chips) and histopathologic outcome parameters (Gleason scores and histologic staging) performed on the subsequent radical prostatectomies (RPs) in a study cohort of 54 patients. Due to tissue loss during arraying and sectioning, a total of 44 (81.5%) tumor samples remained available for immunostaining which was dichotomized by two independent clinical pathologists as being absent or present. MUC1 expression was present in 7 (15.9%) of the 44 IPC immunohistochemically investigated with a striking over-representation in high stage tumors, and was significantly correlated with histopathologic staging (ρ = 0.4; p = 0.02) and Gleason scores (ρ = 0.3; p = 0.03) performed on the corresponding RPs. These data were confirmed by means of the McNemar test (staging: p = 0.01; grading: p = 0.04). Our findings suggest that MUC1 might become a valuable adjunct to enable individual prognostic ramification prior to radical surgery in prostate cancer histologically detected in TURP chips. This interesting observation clearly awaits validation by larger studies surveying clinical follow-up data.