The Historical Evolution of Head and Neck Tumor Pathology in WHO Classifications: From Morphology to Molecular Taxonomy

Purpose The WHO classification of head and neck tumors over the past five decades were reviewed, highlighting the major conceptual and taxonomic changes that have shaped contemporary head and neck pathology. Methods Major WHO classifications of head and neck tumors were reviewed, with a focus on changes in diagnostic concepts and taxonomic principles rather than individual additions or removals of tumor entities. Results WHO classifications have evolved from morphology-based, site-specific systems to an integrated clinicopathological and molecular taxonomy. Early editions emphasized histomorphology and presumed tissue of origin. Subsequent classifications, however, increasingly incorporated immunophenotypic and molecular findings. The recognition of virus-associated neoplasms and recurrent molecular alterations has contributed to defining new entities and refining existing categories. The fifth edition further standardized tumor taxonomy by introducing essential and desirable diagnostic criteria, reflecting a biology-driven approach to classification. Conclusion The evolution of WHO classifications reflects major advances in tumor biology and has substantially influenced diagnostic practice and clinical interpretation. Future classifications will likely incorporate increasingly sophisticated molecular, digital, and computational approaches while maintaining standardized, reproducible, and clinically meaningful diagnostic criteria.