Assessing the applicability and interobserver variability of tumor budding and poorly differentiated clusters in colorectal cancer

Colorectal cancer (CRC) was the third most lethal cancer in 2022 worldwide. Tumor budding (TB) and poorly differentiated clusters (PDC) are prognostic factors. However, the lack of standardization in the assessment and reporting of TB and PDC can hinder their application in the pathologist’s daily practice. This study aims to address these challenges by determining the interobserver variability and the applicability of TB and PDC in CRC. In a 93-patient series, two independent pathologists assessed both variables according to ITBCC guidelines on H&E and AE1/AE3 slides. The overall concordance rate and kappa coefficient were 89.2% and 0.81 for both variables on H&E; for IHC, the results were 69.9% and 0.55 – 88.2% and 0.81 for TB and PDC, respectively. Concluding, H&E analysis had excellent agreement results for TB and PDC, indicating their reproducibility and applicability in the pathologist's daily practice, while AE1/AE3 IHC can still be used in specific situations.