Abstract
Background: Inter-observer variability among pathologists' reports has been a significant challenge in the diagnosis of diseases, especially cancers. Designing a grading system with minimal inter-observer variability can help achieve more accurate diagnoses. Objectives: We aimed to determine whether the grading system proposed by Cheng and colleagues (Cheng’s grading system) can improve inter-observer variability among pathologists in grading urothelial cancer, compared with the World Health Organization (WHO) grading system (2004/2016). Methods: Four pathologists examined all slides of bladder biopsy samples diagnosed as urothelial carcinoma, available in the archives of Imam Reza Hospital, Mashhad, Iran, from 2019 to 2022. Each pathologist reported the tumor grade based on both grading systems, independently of previous answers or the reports of their colleagues. Results: Of 132 samples, the majority were from men (84.1%); the mean age of patients was 66.56±11.31 years. For low and high grades of the WHO system and grade II in Cheng’s grading system, κ = 0.602; agreement was lower for grade III (κ = 0.439) and higher for grade IV (κ = 0.690) compared with the WHO grading system. There was significant agreement among the pathologists in all tumor characteristics, with excellent agreement for stromal invasion (κ = 0.790) and muscular invasion (κ = 0.884), fair to good agreement for WHO 2004/2016 grading (κ = 0.602) and Cheng’s grading (κ = 0.574) overall, and poor agreement for tumor heterogeneity (κ = 0.360). Conclusions: Both grading systems demonstrated favorable agreement among pathologists, without significant differences between the two systems. These results confirm the appropriateness of both grading systems.