Univariate analysis showed significantly positive correlations for growth type, mitosis, perineural invasion, vascular invasion, lymphatic invasion, depth, thickness, and infiltration growth ratio. Multivariate analysis had a significantly positive correlation with nest formation and depth in all patients, and with thickness in patients with T1 or T2. In patients with bilateral cervical lymph node metastasis, lymph node metastasis was significantly positively correlated with perineural invasion.