Narrative review of patterns of lymphatic drainage in early-stage non-small cell lung cancer

: In non-small cell lung cancer (NSCLC), the presence of metastatic nodal disease has been shown to be the most important predictor of long-term disease-specific survival after surgical resection. In patients with early stage, node-negative NSCLC who undergo complete resection, the current standard of care, a significant portion have recurrence of disease within 24 months after surgery. This has raised interest in better understanding the lymphatic drainage of these cancers to determine the exact patterns of loco-regional spread, and whether sentinel lymph node (SLN) identification can be utilized to aid in management of these diseases. Anatomic studies that have attempted to map the lymphatic drainage of tumors from different locations within the lung have revealed patterns of direct mediastinal drainage, which may help explain the prevalence of skip metastases, which is the presence of N2 disease in the absence of N1 disease. This article will provide a narrative review of primary literature concerning the anatomy of the pulmonary lymphatic system, patterns of nodal metastasis in NSCLC as studied through various techniques (including blue dye, radiocolloid tracers, and near-infrared image-guided SLN mapping), and opportunities for improvement in our understanding of how lung tumors interact with the lymphatic system on a structural level.