Diagnostic Significance of Cell Clusters in Voided Urine in SurePath and ThinPrep Liquid-based Cytology.

BACKGROUND: Diagnostic significance of cell clusters (CCs) appearing in voided urine cytology remains unclear. Epithelial malignancy tends to form large clusters but tumor cells get discohesive and clusters become smaller with disease progression. We investigated diagnostic significance of CC in the differentiation between low-grade urothelial carcinoma (LGUC) and high-grade urothelial carcinoma (HGUC) and then HGUC detection. METHODS: Voided urine samples, suspected of new-onset bladder cancer, with corresponding pathological diagnosis were analyzed. Malignancy other than urothelial carcinoma was excluded. Specimens prepared by the SurePath and ThinPrep liquid-based cytology methods were analyzed separately. Cytological diagnosis was based on The Paris System 2.0 and maximal CC size was measured. These data were subject to statistical analysis. RESULTS: 123 SurePath and 168 ThinPrep cases were analyzed. Cytological diagnosis was significantly associated with pathological diagnosis in both SurePath and ThinPrep specimens. Then, CC was found to be present in approximately 60% of specimens prepared by both methods. There was no significant difference in CC size among benign lesions, LGUC, and HGUC in both SurePath and ThinPrep specimens. Meanwhile, high-risk cytology which consists of Suspicious for HGUC and HGUC based on TPS 2.0 demonstrated similarly high specificity and positive-predictive value for HGUC detection irrespective of CC presence/absence but sensitivity was significantly higher when CC was present in both SurePath and ThinPrep specimens. CONCLUSION: Size of CC was not useful for differentiating LGUC from HGUC, but CC presence was advantageous for detecting HGUC possibly due to a sufficient amount of collected cells for diagnosis.