[HEAD AND NECK MALIGNANCIES CLASSIFICATION, THE 8TH EDITION OF THE AMERICAN JOINT COMMITTEE ON CANCER - WHAT IS NEW?].

The American Joint Committee on Cancer (AJCC) staging manual has become the point of reference for classifying patients with cancer, defining prognosis, and determining the best treatment approaches. The eighth edition of the Head and Neck AJCC Cancer Staging Manual incorporates significant changes based on advances in our understanding of the etiology and certain histologic attributes of tumors. Changes were made only when there was strong evidence for inclusion, while balancing between "population-based" and a more "personalized" approach. We describe the main changes implanted into the AJCC 8th edition while analyzing the effects on treatment plans and survival metrics. 1. The most significant update, to better reflect the variety of diseases arising in the pharynx, creates a separate staging algorithm for high-risk human papillomavirus-associated cancer of the oropharynx. Therefore, pharynx carcinoma has been divided into 3 separate chapters - nasopharynx, high-risk HPV-associated (p16-positive) oropharynx, and hypopharynx and non-high risk HPV-associated (p16-negative) oropharynx. 2. Another important update incorporates extra nodal extension as a prognostic variable for regional lymph node metastases in non-viral associated head and neck tumors. 3. Significant changes to the tumor (T) categories for oral cavity are discussed, where, for every 5-mm increase in depth of invasion (DOI), categories will increase one level, demonstrating better consistent and predictive survival curves. 4. A major tumor (T) category change for nasopharyngeal squamous cell carcinoma (SCC), regarding the prevertebral and pterygoid muscles, is discussed. We go through the rationale behind the major changes while practicing the new staging system among different cases.