Objective To investigate the frequency of micrometastasis in levels Ⅲ-Ⅳof clinical negative neck（cN0） in patients with squamous cell carcinoma（SCC） of oral tongue, and to discuss the management of cervical lymph node for cN0 tongue SCC. Methods A total of 471 cervical lymph nodes derived from 25 patients with cN0 tongue SCC, including 263 lymph nodes in level Ⅲ and 208 lymph nodes in level Ⅳ, were included in this study. All lymph nodes were re-examined by anti-cytokeratin （CK） immunohistochemical staining combined with semi-serial section per 500 μm. Results Among the 25 cases, seven patients were confirmed harboring metastasis in 11 lymph nodes of level Ⅲ, and no positive lymph node in level Ⅳ was detected by routine hematoxylin-eosin（HE）staining. 11 positive lymph nodes in level Ⅲ, which confirmed by HE staining, were also detected by immunohistochemical staining with CK combined with semiserial section. Among the 460 cervical lymph nodes in which HE staining did not show metastasis, only one lymph node in level Ⅲharboring a 2.0 mm×1.5 mm micrometastasis was detected by immunohistochemical staining with CK, and no positive lymph node in level Ⅳ was detected by immunohistochemical staining with CK. Conclusion The frequency of occult metastasis in level Ⅳ was very low, so it seemed unnecessary to dissect level Ⅳ for all patients with cN0 tongue SCC.
