International consensus recommendations and alignment of terminology for the histopathological diagnosis of extranodal extension in head and neck squamous cell carcinoma: an HN-CLEAR initiative

Histopathologically detected extranodal extension leads to upstaging and treatment escalation in head and neck squamous cell carcinoma. There is considerable variation in the prevalence of histopathologically detected extranodal extension in comparable studies. The Head and Neck Cancer International Group, which includes 23 organisations managing patients with head and neck cancer, identified several challenges in evaluating histopathologically detected extranodal extension. Thus, the Head and Neck Consensus Language for Ease and Reproducibility (HN-CLEAR) and its global stakeholders prioritised developing diagnostic criteria and uniform terminology for histopathologically detected extranodal extension. The histopathologically detected extranodal extension working group established by WHO, International Collaboration on Cancer Reporting, American Joint Committee on Cancer, Union for International Cancer Control, North American Society of Head and Neck Pathology, and American Academy of Oral and Maxillofacial Pathology committees undertook consensus deliberations using scanned whole slides and a PRISMA literature review-based scoping questionnaire. The guidelines were tested by 30 additional pathologists across six continents and strengthened with prescriptive diagnostic criteria and unifying terminology based on the inter-rater concordance analyses. This Review generates practically useful consensus diagnostic recommendations and aligned terminology for addressing the gaps in the histopathologically detected extranodal extension literature. The recommendations can be used globally and cater to all levels of medical resources, practices, and experiences, thus ensuring equitable patient care.