CONCLUSION: High correlation between clinical and pathological stages for assessment of mandibular invasion and neck metastasis supports the reliability of CT in our study. Diagnostic contribution of magnetic resonance imaging is necessary for assessment of extrinsic tongue muscle involvement; in cases of tongue cancer which are surrounded by induration on palpation and extending to the floor of the mouth.OBJECTIVES: This study aims to compare the clinical and pathological TN stages of patients with oral cavity cancer and to identify the factors leading to staging discrepancies.PATIENTS AND METHODS: The medical records of 125 patients (77 males, 48 females; mean age 57 years; range 19 to 82 years) who underwent primary tumor resection and neck dissection simultaneously for oral cavity cancer were retrospectively analyzed. Clinical and pathological TN stages of all patients were compared. Sensitivity, specificity and predictive values of clinical staging were calculated.RESULTS: Computed tomography (CT) with contrast which was used to examine the cervical lymph node metastasis showed a sensitivity of 71.9%, a specificity of 75%, a positive predictive value of 70.6%, and a negative predictive value of 76.1%. The diagnostic accuracy of CT for detecting mandibular invasion was as follows: sensitivity, 92.6%; specificity, 97%; positive predictive value, 96.1%; and negative predictive value, 94.3%.