A new seven-point method facilitates accurate diagnosis of high-grade urothelial carcinoma in routine urinary cytology practice

Abstract Introduction This study was designed to identify the minimal and necessary cell morphologies to be considered for high-precision diagnosis of high-grade urothelial carcinoma (HGUC) in a routine urinary cytology practice. Materials and Methods We included 338 urine cytology specimens from 11 medical facilities in Japan. Six experts evaluated these Papanicolaou-stained specimens using their own diagnostic criteria to categorize them within an initial four-tiered classification system. Of the 338 cases, 70 HGUC and 32 benign cases, with a complete consensus diagnosis of six experts, were included for the analysis. Two of the cytologists evaluated the specimens for 20 specific cellular features. The results were analyzed using a contingency table and by discriminant analysis. Results Of the original 338 cases, 165 were originally diagnosed as HGUC, but only 70 (42.4%) were scored as malignant by all participating cytologists; of the 101 benign cases, only 32 (31.7%) were classified as such in all examinations. These specimens were re-evaluated by six experts using a panel of 20 specific cellular features used to distinguish between HGUC and benign diseases; tests of significance and discriminant analyses identified seven critical features that were most useful for cytological diagnosis. Statistical analysis revealed that a focus on these seven features led to a diagnosis of HGUC with a probability of over 95%. Conclusions The accuracy of our presently used method to evaluate urinary cytology is not consistently high. This novel classification system, which focuses on seven critical features, facilitates the high accurate diagnosis of HGUC in routine cytology practice.