Abstract
The AJCC/UICC TNM staging system was revised to the 8th edition. In this study, we analyzed the prognosis and risk of occult nodal metastasis in patients with tongue cancer to validate the usefulness of the 8th edition TNM classification. Ninety-two patients with tongue cancer diagnosed as T1-T2N0M0 according to the 7th edition of the TNM classification were evaluated for clinicopathological findings, overall survival, diseasespecific survival, and occult lymph node metastasis. The 5-year overall and disease-specific survival rates for all patients were 79.4% and 91.0% respectively. When reclassified based on the 8th edition T classification, 13 T1 patients were reclassified to T2 and 6 T2 patients were reclassified to T3. Multivariate analysis revealed that differentiation, local recurrence, and occult cervical lymph node metastasis were factors associated with overall survival. Of these, occult cervical lymph node metastasis was significantly associated with depth of invasion and tumor budding in a multivariate analysis. The 8th edition T classification considering the degree of depth was considered useful. These results suggest that the poor prognostic factors for early-stage tongue cancer are primary recurrence and occult neck metastasis, and that the 8th T classification reflecting the degree of depth is useful for predicting occult neck metastasis.
