Global Proposal for the TNM Staging System for Poorly Differentiated Thyroid Cancer.

A PDTC-specific TNM staging system reclassifies level VII lymph node metastasis and improves prognostic discrimination, with C statistics rising from 0.71 to 0.74 in the IATCCG cohort.

• Why it matters: Poorly differentiated thyroid cancer lacks a dedicated staging framework, so clinicians must rely on TNM-8 designed for differentiated disease despite distinct biology and prognostic patterns.
• What they did: Using IATCCG data from 91 centers across 14 countries (1010 surgically treated patients), the team refit TN combinations in multivariable Cox models for overall survival, selecting the lowest Akaike information criterion configuration and validating in US SEER (170 patients).
• The result: Level VII LNM showed lower 5-year overall survival (45.2%) than level VI (73.2%) or lateral neck LNM (56.7%), leading to reclassification from N1a to N1c; the proposed system increased stage IV share (18.5% to 32.4%) and improved C statistics versus TNM-8 (IATCCG: 0.74 vs 0.71; SEER: 0.76 vs 0.74).

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