[Mediastinal lymphatic spread of bronchopulmonary cancer]

The mediastinum may be divided into 4 zones divided by the tracheo-bronchial axis in which are situated the lymphatic chains involved in the lymphatic drainage of the lungs. In the upper right zone there are 2 chains which are frequently involved, the right paratracheal chain (PTD) and the tracho-oesophageal chain (TO) and 2 lymphatic chains which are less often involved, the superior right phrenic chain (PH Dt) and the lymphatic chain which crosses the Azygos vein (AZM). In the superior left zone are found 2 chains which are frequently infiltrated: The pre-aortic carotid chain (AO) and the left superior bronchial chain (BSG) and 2 chains which are more rarely involved: The left superior phrenic (PHG) and the chain which crosses the aorta (the minor aorta Azygos; AOmi). At the level of the right and left inferior zones are found important groups of lymphatic ganglia at the intratracheo-bronchial bifurcation (ITB) and of one other part of the tracheo-oesophageal axis, the juxta-oesophageal ganglia (OE) and those of the triangular ligament (LT). The lymph coming from the pulmonary segments crosses the ganglia (LN) of the segments of the lobe and of the hilum before reaching the mediastinum and then at the final stage the lymph nodes situated on the margins of the mediastinum considered as N3 in cancer assessment. This schema is not the rule. In less than 5% of cases the lymph may drain without any lymph node relay either to the subclavicular hollow or to the thoracic duct in the mediastinum. More frequently (in 20-35% cases according to the segment considered) the lymph returns directly to the mediastinum ganglia without relaying through the intrapulmonary ganglia. Finally there are those cases where only the perilobar LN are involved. In these cases it is not necessarily the LN of the lobe drained but sometimes of another pulmonary lobe. These direct paths (N2) confirmed in study of cancer, demand and justify the need for a systematic cure of mediastinal LN. It is equally important to achieve a cure in the remaining lobes in the case of a lobectomy and not to fail to recognise an N1 state.(ABSTRACT TRUNCATED AT 400 WORDS)