Diagnostic immunocytostaining with Peroxisome Proliferator-Activated Receptor-Gamma in urine cytology samples

Introduction: Urine cytology is a common method for detection of urothelial carcinoma (UC), however, is not high sensitivity. Improvement of the accuracy of cytodiagnosis using immunocytostaining as an auxiliary method is needed. This study aimed to determine the cyto-diagnostic usefulness of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) immunocytostaining in urine cytology for the detection of urothelial carcinomas, particularly low-grade urothelial carcinomas (LGUC).Methods: PPAR-gamma immunocytostaining was performed for 37 urothelial carcinoma (UC) cases and 26 benign cases. Among the UC cases, 22 cases were of the papillary proliferation type, not including the mixed type comprising both papillary and flat growth. Fifteen LGUC cases of all papillary proliferation types were included. For comparison, the same samples were also immunocytostained for p53 and Ki-67.Results: Of the UC cases, 25 of 37 were positive for PPAR-gamma, while 24 of the 26 benign cases were PPAR-gamma-negative. Regardless of histological grading, 13 of the 22 UC cases with papillary proliferation were PPAR-gamma-positive. In particular, PPAR-gamma immunocytostaining showed higher sensitivity for LGUC cases than that of the other biomarkers. Regarding LGUC specifically, 4 of 10 cases not identified by primary cytology were detected by PPAR-gamma immunocytostaining. Conclusion: PPAR-gamma immunocytostaining enhances the accuracy of urine cytodiagnosis. Furthermore, PPAR-gamma is a more useful immunobiomarker in urine cytology than p53 and Ki-67, the commonly used immunobiomarkers for malignant cell detection.