Prediction of skip mediastinal lymph node metastasis in surgical patients with clinical N0 non-small-cell lung cancer.

e18554 Background: It has been reported that the prognosis of surgical non-small-cell lung cancer (NSCLC) patients with skip-N2 metastasis (without hilar lymph node metastasis) is generally more favorable than that of those with pathological N2 disease. Therefore, when a surgeon determines whether to perform mediastinal lymph node dissection, it is important to accurately predict skip-N2 metastasis in surgical patients without hilar lymph node metastasis. Methods: Of the patients who had undergone complete resection for NSCLC in our hospital between October 1986 and December 2010, 741 with cN0 NSCLC who had undergone mediastinal lymph node dissection were analyzed. The relationship between the lymph node metastasis status and clinicopathological parameters (age, gender, and serum CEA level, histological type, primary tumor location, tumor diameter, pleural invasion(pl), lymphatic invasion(ly), vascular invasion(v)) was analyzed, and factors that predict differences between pN0 and skip-N2 patients were identified. Results: Of the 741 patients, 609 had pN0 disease, 62 pN1 disease, and 70 pN2 disease. Of the pN2 patients, 23 had skip metastases to the mediastinal nodes alone. No significant difference was observed in the gender, age, or histological type between the N0 and skip N2 groups. However, the serum CEA level, tumor diameter, and pl(+) rate were significantly higher (p=0.0028), larger (mean, 3.7 cm, p=0.012), and higher (p=0.0064), respectively, in the skip-N2 group. Also, the ly(+) and v(+) rates were significantly higher in the skip-N2 group. Skip-N2 appeared more frequently with primary tumors in the lower lobes than with those in the upper lobes. Conclusions: Even if no hilar lymph node metastasis is found during surgery in patients with a high serum CEA level, large tumor diameter or lower lobe location, they may have skip-N2 lymph node metastasis. Although the p factor status becomes clear after surgery, patients with pleural indentation so marked as to raise the suspicion of pl(+) have a high probability of skip-N2 metastasis. Mediastinal lymph node dissection is preferable in these patients.