This retrospective study was based on 237 patients with non-small cell lung cancer (NSCLC) and nodal N2 disease. All accessible mediastinal lymph nodes (LN) were removed and classified according to their anatomical location in LN chains. The pulmonary resections performed were: pneumonectomy (n = 187), lobectomy (n = 44) and segmentectomy (n = 4). There was solitary nodal chain involvement by metastasis in 141 cases, two chains in 72 cases and three or more in 24; "skip" metastases were present in 26.6%. N2 disease would have been missed in 45 cases of single chain involvement (31.9%) if routine removal of mediastinal nodes had not been performed. The overall 5-year survival rate was 18.8%. Survival was not influenced by site, size or extension (T) of tumor, tumor histology or the presence of vascular invasion. The prognosis was significantly worsened by the presence of microscopic residual disease (30 cases) and of satellite nodules (23 cases). Survival was significantly improved when metastases involved a single LN chain (26.3 versus 8.3%, P = 0.0003). The location and number of involved nodes in the chain, "skip" metastases and the presence of extracapsular spread of carcinoma did not influence the prognosis. Routine mediastinal LN dissection is necessary to improve survival and for classification of lung cancer. Anatomic description allows better understanding of N2 disease which is not a contraindication to surgery when a gross complete resection can be achieved.
Correlation of the anatomic and surgical features in 360 cadavers and in 260 patients operated for bronchial carcinoma reveals that the lymphatics of the lung reach the ipsilateral mediastinum, sometimes directly and sometimes by sites which do not correspond to the anatomic site of the injection or of the pulmonary lesion. This implies the need for systematic eradication of all the lymph nodes of the ipsilateral mediastinum during surgery for bronchial carcinoma. In cases of tumoral lesions (N2), the prognosis is better when only one site is involved, whether the nodal disease is microscopic, uni- or multiglandular, with or without rupture of the capsule and whatever treatment is carried out, even when resection seems macroscopically complete to the surgeon. This is explicable in the light of the anatomic study, which shows that the lymph node chain is a functional entity which channels the lymph into the systemic circulation, either at the venous confluence of the neck or into the thoracic duct in the mediastinum. When only a single chain is affected, there is a greater than 70% chance that systemic metastases are already present, 90% when N2 affects 2 chains, while in N3 cases (lymph passage to contralateral chains) the incidence reaches virtually 100%. However, macroscopically satisfactory excision allows management of the local problem, and involvement of the mediastinal nodes, even with capsular rupture, cannot be considered as a contraindication in the absence of clinically detectable systemic metastases.
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