Interobserver agreement in grading of colorectal cancers-findings from a nationwide web-based survey of histopathologists

Aims: Tumour grade represents a gestalt of all molecular changes in malignancy, reflecting aggressiveness and has been shown to add prognostic information independent of stage for many malignancies, including colorectal cancer. Despite the grade of colorectal cancer being reported routinely in the UK, there is paucity of data on the level of agreement between histopathologists and hence the value of this metric in clinical practice. The aim was to estimate the degree of inter-observer variation in grading by conducting a nationwide web-based survey of histopathologists. Methods and results: Individuals were asked to grade a series of 20 tumours. Data from 104 pathologists surveyed indicates that agreement using both two and three grade systems is at best fair. Conclusions: Given that for the foreseeable future the histopathological criteria of stage and grade will still provide the mainstay of prognostication and therefore clinical decision-making, efforts should be made to improve grading criteria and standardize use of the low- and high-grade categories.