Diagnostic value of urine cytology in detecting histologic variants of urothelial carcinomas in the urinary bladder: Cytopathologic correlation of 72 cases

Background: Precise identification of histologic variants in urothelial carcinoma (UC) is important because some histologic types have a poor prognosis and clinical management varies. Urine cytology is used for bladder cancer screening, but the cytomorphologic features of histologic variants have not been well described. In the current study, we evaluate the effectiveness of urine cytology in detecting histologic variants of UC in the urinary bladder. Methods: Seventy-two urine cytology specimens from patients diagnosed with high-grade UCs by radical cystectomy were retrospectively reviewed and correlated with histopathologic findings of subsequent radical cystectomy specimens. Results: Of 72 total cases, 24 (33%) cases showed six histologic variants in corresponding surgical specimens, including squamous differentiation (13 cases), plasmacytoid variant (3 cases), micropapillary variant (3 cases), sarcomatoid variant (3 cases), giant cell variant (1 case), and glandular differentiation (1 case). Histopathology and cytomorphology were well correlated in 13 cases (54%), with squamous differentiation in 11 of 13 cases (85%), micropapillary features in 1 out of 3 cases (33%), and spindle cell/sarcomatoid features in 1 of 3 cases (33%). Furthermore, mucosal involvement by histologic variants, not amount of histologic variant, was related to high concordance rates between cytology and histology diagnosis. Conclusions: The morphologic features of some histologic variants of high-grade UCs, such as squamous differentiation, micropapillary variant, and sarcomatoid variant, are partially reflected on urine cytology. In addition, mucosal involvement by histologic variants was associated with a higher detection rate of histologic variants in urine cytology.