Imaging-Detected Extranodal Extension in Head and Neck Cancer: Clinical Significance and a Standardized Imaging Assessment

Extranodal extension (ENE) is an important adverse prognostic factor in head and neck cancer and has significant implications for treatment planning. Traditionally, pathologic ENE has guided nodal staging and postoperative management; however, its assessment is limited to surgically treated patients. In contrast, imaging-detected ENE (iENE) can be evaluated before treatment in all patients, regardless of treatment modality, underscoring its growing clinical relevance. Despite this advantage, variability in imaging interpretation has persisted due to the lack of standardized definitions and diagnostic criteria. Recent international consensus efforts have addressed this gap by proposing standardized terminology and a tiered classification system for iENE to enhance reproducibility and clinical communication. This review summarizes the concept and clinical significance of iENE from a radiologist's perspective, examines the limitations of previously proposed imaging criteria, and provides a stepwise explanation of the standardized classification system. Practical considerations for applying this system in routine radiologic interpretation and reporting are also discussed.