MUC1 Expression in Incidental Prostate Cancer Predicts Staging and Grading on the Subsequent Radical Prostatectomy Sven Gunia & Matthias May & Stefan Koch & Manfred Dietel & Andreas Erbersdobler Received: 5 October 2009 / Accepted: 16 November 2009 / Published online: 27 November 2009 # Arányi Lajos Foundation 2009 Abstract 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 inde- pendent 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 corre- sponding 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. Keywords Incidental prostate cancer . MUC1 (episialin) . Immunohistochemistry . Histopathologic outcome parameters . Radical prostatectomy Introduction Incidental prostate cancer (IPC) is defined as a clinically unapparent tumor discovered after histologic examination of the specimen obtained by open prostatectomy or transure- thral resection (TURP chips) of the prostate [1]. Its overall incidence in TURPs performed for clinically benign prostatic hypertrophy varies between 13% and 22% [2]. The currently established subdivision of the disease into two histopatho- logic stages (T1a and T1b) according to the latest TNM classification system has gained wide acceptance [3]. However, owing to its substantially variable natural history, clinical management (“wait and watch” versus radical surgery) remains challenging since the clinical course of individual IPC cannot be predicted by means of conventional histopathology. Especially, there is often disagreement between the Gleason score at TURP and prostatectomy [4]. Therefore, advanced predictive factors are clearly needed in order to better define the individual course of the disease. Mucins are increasingly used as diagnostic markers as well as possible therapeutic targets due to their aberrant expression pattern during cancer progression. Seven genes S. Gunia (*) : S. Koch Department of Pathology, HELIOS Klinikum Bad Saarow, Charité-University Medicine Teaching Hospital, Pieskower Straße 33, 15526 Bad Saarow, Germany e-mail: sven.gunia@helios-kliniken.de M. May Department of Urology, Klinikum St. Elisabeth, Straubing, Germany M. Dietel : A. Erbersdobler Department of Pathology, Charité-University Medicine, Campus Charité Mitte, Berlin, Germany Pathol. Oncol. Res. (2010) 16:371–375 DOI 10.1007/s12253-009-9231-4