Radiological assessment of extranodal extension in patients with head and neck squamous cell carcinoma

The prognosis of patients with head and neck squamous cell cancer (HNSCC) decreases with the presence of extranodal extension (ENE) in lymph node metastases. Therefore, ENE was introduced in the 8th Edition TNM Classification (TNM8) for Head and Neck Cancer as a staging variable in all HPV-negative HNSCC. Patients with ENE may benefit from adjuvant or even primary chemotherapy and/or radiotherapy. There is a clear discrepancy between the definition of clinical ENE and pathological ENE. In TNM8, the radiological evaluation of ENE only plays a supportive role. Since not all patients with advanced disease will undergo a neck dissection, histologic proof of ENE will not always be available. In these cases, it would be of great help to be able to accurately determine ENE with radiological imaging. In this review, an update is given of the ability of radiological imaging to identify and grade ENE.