Potential pitfalls within the AJCC 8th Edition Staging System for Salivary Gland Carcinoma

Abstract

Salivary gland carcinomas (SGCs) are uncommon malignancies, representing less than 5% of all head and neck cancers. They exhibit marked variation in their histological types, as well as in clinical and biological behavior. According to the 5th edition of the World Health Organization (WHO) Classification of Head and Neck Tumours (5th ed.), in the chapter on salivary gland tumors, there are 21 recognized types of SGCs. The prognosis of patients with SGCs is currently assessed using the Tumor, Nodes, Metastasis staging system established by the American Joint Committee on Cancer (AJCC). However, recent evidence indicates that this system may lack sufficient sensitivity in predicting treatment response and survival outcomes, particularly with respect to cervical nodal involvement. Notably, the 8th edition of the AJCC staging protocol applies the same N-classification to both human papillomavirus-negative squamous cell carcinoma of the upper aerodigestive tract and SGCs, despite marked differences in biological behavior, therapeutic strategies, and clinical outcomes between these entities. The pitfalls in the 8th AJCC N-staging system for SGCs include the lack of prognostic significance of extranodal extension, the lack of consideration of parotid lymph nodes, and the significance of bilateral neck metastases, which are extremely rare in SGCs. The aim of the present narrative review was to highlight the unresolved limitations of the AJCC 8th edition.

Keywords: salivary gland carcinoma; staging; classification; pathological nodal status; depth of invasion