Background: The relationship between the histological parameters of primary lesions and lymph node metastasis in supraglottic and hypopharyngeal cancers has not been elucidated. This analysis is important to evaluate the requirement for additional elective neck dissection when clinically node-negative cancers are treated by transoral surgery. Methods: This study included 40 previously untreated patients with supraglottic and hypopharyngeal cancers who underwent transoral en bloc tumor resection in two academic tertiary referral centers. Nodal status was confirmed by neck dissection for cases with findings or suspicion of lymph node metastases or by observation of clinically node-negative cases for more than 1 year. Patients' medical records and pathological features were analyzed retrospectively. The correlation of histological parameters with lymph node metastases, including occult metastases, was evaluated by univariate and multiple logistic regression analyses. Results: Univariate analysis showed that lymph node metastasis was correlated with tumor depth (P = 0.00087) and venous invasion (P = 0.027). Multiple logistic regression analysis showed that it was significantly correlated only with tumor depth (P = 0.007). Conclusions: Tumor depth is the most useful parameter for predicting lymph node metastases. In clinically node-negative cases, when tumor depth exceeds 1 mm, elective neck dissection must be considered and, when it is less than 0.5 mm, regular clinical follow-up is recommended. Patients with tumor depth between 0.5 and 1 mm should be carefully observed, since they also have a chance of developing nodal metastasis. Venous invasion also indicates high rates of nodal metastasis, therefore elective neck dissection must be considered for these cases.
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