Expression of MUC1 (Ma695) in noninvasive papillary urothelial neoplasm according to the 2004 World Health Organization classification of the noninvasive urothelial neoplasm. An immunologic tool for the pathologist

OBJECTIVE: To examine the association between MUC1 (Ma695) and noninvasive papillary urothelial neoplasm according to the 2004 World Health Organization classification. STUDY DESIGN: Histologic evaluation was performed in 46 patients with nontumoral benign bladder urothelium (n = 11), papillary urothelial neoplasm of low malignant potential (PUNLMP) (n = 14), low-grade papillary urothelial carcinoma (LgPUC) (n = 11), and noninvasive high-grade papillary urothelial carcinoma (HgPUC) (n = 10). Classical morphologic description and semiquantitative digital measurement were performed from immunohistochemical-stained slides using an anti-MUC1 antibody (Ma695). RESULTS: Measures showed an obvious statistical difference between benign urothelium and LgPUC (p = 0.0004) or HgPUC (p = 0.0041). MUC1 is expressed less in PUNLMP than in LgPUC (p = 0.04). Benign urothelium and PUNLMP more often showed apical and superficial MUC1 expression. Basal cells with cytoplasmic and/or circumferential membrane positivity were more often observed in LgPUC and HgPUC (p < 0.001). CONCLUSION: MUC1 could be an interesting tool for the pathologist to differentiate between PUNLMP and LgPUC or HgPUC.