Original articleDiagnostic utility of Ki-67 immunohistochemistry in small endoscopic biopsies of the ureter and renal pelvis

Diagnosis of upper urinary tract urothelial carcinoma in ureteroscopic biopsies is challenging. Therefore, an immunohistochemical marker that can differentiate between malignant and benign urothelium and predict final pathological features is necessary. In this study, we investigated Ki-67 expression in 26 ureteroscopic biopsies of the ureter and renal pelvis diagnosed with urothelial carcinoma (UC) and in 13 biopsies with non-neoplastic urothelium, using digital image analysis. The median Ki-67 labeling index was 1.5% (range: 0.2-13.9%) in non-neoplastic urothelial specimens and 15.0% (range: 0.2-61.3%) in UC specimens (p = 0.0001). In 12 of 26 (46%) UC specimens, the Ki-67 labeling index was more than 20%. By contrast, the Ki-67 labeling index was less than 5% in 11 of 13 (85%) non-neoplastic urothelial specimens. Ki-67 expression in ureteroscopic biopsies was significantly correlated with high tumor grade (p = 0.013), concomitant carcinoma in situ (p = 0.011), and stromal invasion (p = 0.048) in surgical resection specimens. Our data suggested that Ki-67 may provide supplemental, objective evidence that can aid diagnosis of upper urinary tract UC in ureteroscopic biopsy specimens. Determination of Ki-67 expression in ureteroscopic biopsy specimens is potentially helpful in clinical decision making for patients with suspected upper urinary tract UC.