Objective  To investigate the correlation of lymph node metastasis with the age, gender, smoking index, tumor size, site of the tumor, histopathologic types, and the degree of cell differentiation of primary non-small cell lung cancer (NSCLC), and characterize the incidence and distribution of mediastinal lymph node metastasis.

  Methods  Clinicopathologic analysis of 96 patients who underwent surgery for non-small cell lung cancer (NSCLC) and lymph node dissection was performed in this study.

  Results  Nodal metastasis was not related to age, gender, and smoking index. No statistically significant differences in the incidence of lymph node metastasis were observed among tumors of different sizes. The incidence rates of nodal metastasis were 15.8%, 47.8%, and 59.0% in well-differentiated, moderately differentiated, and poorly differentiated carcinoma, respectively. The lower the degree of tumor differentiation, the higher (P < 0.05) was the incidence of mediastinal lymph node metastasis. No correlation was observed between histopathologic type and lymph node metastasis. The N2 metastatic rates of squamous cell carcinoma and adenocarcinoma were 13.6% and 34.0%, respectively. Mediastinal lymph node metastasis was more commonly seen in lung adenocarcinoma than in squamous cell carcinoma (P < 0.05). No statistically significant differences in the incidence of mediastinal lymph node metastasis were observed between central and peripheral lung cancers. Skip N2 metastasis occurred in 12 of the cases, whereas skip mediastinal nodal metastasis occurred in the other 9. Cross-regional mediastinal metastasis frequently occurred in lung cancer and no significant differences in the cross-regional mediastinal metastasis were observed between the lower and upper lobes (P < 0.05).

  Conclusion  The lymph node metastasis of NSCLC is closely correlated with the degree of cell differentiation, but is not with age, gender, smoking index, histopathologic type, and the size of the primary tumor. Mediastinal nodal metastasis was more commonly seen in lung adenocarcinoma than in squamous cell carcinoma. Most of the lymph node metastases in lung cancer were consistent with the following distribution: from the near to the distant, from top to bottom, and again from inside the lungs to the mediastinum via the hilum. Systematic dissection of the intrathoracic lymph nodes was needed as pulmonary resection was conducted.