Grading variability of urothelial carcinoma: experience from a single academic medical center

Tumor grade plays a critical role in the management of papillary non-invasive urothelial carcinoma (UC). Since grading of UC relies on morphologic criteria, variability in interpretation exists among pathologists. The objective of this study was to examine inter-observer variability in the grading of papillary non-invasive UC at a single academic medical center.

One general pathologist and two genitourinary pathologists were blinded to patient identity and graded 98 consecutive UC specimens using the 1973 and 2004 classification systems. Kappa statistics (κ) were used to measure inter-observer reproducibility to account for agreement expected purely by chance. By convention, ϰ values from 0.21-0.4 represent "fair", from 0.41-0.6 represent "moderate", and > 0.6 represent "substantial" agreement.

Raw percentage agreement among all three pathologists was only 26% using the 1973 system and 47% using the 2004 system. When measured by kappa, overall agreement was only "fair" for both systems and while higher for the 2004 system than the 1973, this was not significant (: 0.38 versus 0.26, respectively). There were no significant differences in agreement when comparing the specialists agreement between themselves with agreement between each specialist and the generalist (ϰ: 0.31-0.37 versus ϰ: 0.18-0.46).

The current grading system continues to demonstrate challenges in reproducibility among general and specialized pathologists. The degree of variability has significant implications on management decisions for non-invasive UC. Our findings underscore the need to identify molecular markers that can provide a more objective and reliable risk stratification system to guide patient management.