Abstract
Multiple studies have identified limitations in the nodal (N) category definitions of the eighth-edition tumor-node-metastasis classifi cation (TNM8) for major salivary gland carcinoma (SGC). Minor SGCs have traditionally been staged according to site of origin despite distinct biology and patterns of spread, and the feasibility of a unified staging system for both major and minor SGCs had not been systematically evaluated. These shortcomings prompted a comprehensive reassessment of SGC staging.
A multidisciplinary international expert panel, in collaboration with the American Joint Committee on Cancer (AJCC) Head and Neck Core Group, developed and validated a refined TNM classification for SGC. The proposed system was subsequently adopted by both the AJCC and the Union for International Cancer Control (UICC).
The ninth edition (TNM9) introduces the first unified SGC-specific staging system applicable to both major and minor SGCs. Key revisions include: (1) exclusion of extremely rare or non-salivary-origin histologies (e.g., squamous cell carcinoma, neuroendocrine carcinoma, and basosquamous carcinoma); (2) integration of major and minor SGCs into a single staging framework, with clarification of T3-T4 definitions to ensure applicability across both groups; (3) simplified N categorization based on lymph node count and extranodal extension (ENE): N0 (no nodal disease), N1 (1-3 nodes without ENE), and N2 (3 nodes or any ENE); and (4) restriction of stage IV exclusively to M1 disease, allowing future refinement of metastatic subcategories. Clinical TNM (cTNM) applies the same criteria as pathologic TNM (pTNM), incorporating radiologic assessment of abnormal lymph node count and imaging-detected ENE (iENE).
By establishing a unified, biologically relevant staging system with improved prognostic discrimination, TNM9 enhances clinical applicability and promotes more consistent management of both major and minor salivary gland carcinomas.