Immunostaining as a diagnostic aid in cytopathologic study of upper urinary tract urothelial carcinoma.

OBJECTIVE: To evaluate preoperative diagnosis of low-grade urothelial carcinoma (LGUC) and urothelial neoplasms of unknown malignant potential (UMP UN) of the upper urinary tract (UUT) and its role in disease management, especially in the context of nephron-sparing treatment possibilities. STUDY DESIGN: Wash and brush ureteral specimens of LGUC/UMP UN of the UUT with histopathologic correlation were retrieved at our institution for 7 years and studied along with 7 ureteral specimens from nonneoplastic ureteral lesions. RESULTS: Of 30 specimens from 25 LGUC/UMP UN, 5 were negative for tumor cells and 3 showed cytologic atypia. The remaining 22 contained tumor cells with characteristic features of urothelial carcinoma, including hard and soft criteria. The 4 hard criteria included branching stromal cores, dyshesive cell networks, 3-dimensional papillary clusters with stromal core and atypia associated with CK20-positive cells. The 2 soft criteria were hypercellularity and atypia in CK20-negative cells. All LGUC/UMP UN of the UUT were associated with at least 1 hard criterion or both soft criteria. CONCLUSION: Branching stromal cores, 3-dimensional papillary clusters, dyshesive cell networks and CK20-positive atypia immunostaining appear specific for LGUC/UMP UN of the UUT but are seen in few cases. Combined soft and hard criteria will increase sensitivity to 83%.