Inter- and Intrarater Reliability and Agreement Among Danish Head and Neck Pathologists Assessing Extranodal Extension in Lymph Node Metastases from Oropharyngeal Squamous Cell Carcinomas

Background: Extranodal extension (ENE) in lymph node metastases is one of the most important prognostic factors in head and neck squamous cell carcinomas. Studies have shown inconsistency among pathologists in the assessment of ENE. The aims of this study were: (1) to determine the interrater and intrarater reliability and agreement in the assessment of ENE among Danish pathologists and (2) to test if a standardized assessment method may increase interrater agreement. Methods: Four Danish head and neck pathologists assessed ENE presence or absence in 120 histological slides from lymph nodes with oropharyngeal squamous cell carcinoma metastases (first round). Subsequently, guidelines were introduced to the pathologists and a new assessment was performed (second round). Finally, two of the pathologists assessed the slides to determine intrarater reliability and agreement (third round). Results: Interrater kappa coefficients varied between 0.57 and 0.67 in the first round and between 0.59 and 0.72 in the second round. The intrarater agreement between round 2 and 3 was 0.88 for pathologist 1 and 0.92 for pathologist 2 with resulting kappa coefficients of 0.76 (95% CI 0.64–0.88) and 0.84 (95% CI 0.74–0.94), respectively. Conclusion: We found a moderate level of reliability and agreement among pathologists for ENE in lymph node metastases from oropharyngeal squamous cell carcinomas. The intrarater reliability and agreement was generally higher than interrater measures. Interrater agreement was slightly improved by standardized assessment.