Detection of pleural lymph flow using indocyanine green fluorescence imaging in non-small cell lung cancer surgery: a preliminary study

Abstract

Lymphatic spread of lung carcinoma to the mediastinum is a key determinant of prognosis. The lymph flow often carries metastases from the pulmonary segment directly into the mediastinal lymph nodes, without passing through the hilar nodes. This phenomenon is termed as "skip metastasis." This study investigated the subpleural lymphatic flow to the mediastinum using indocyanine green (ICG) with a near-infrared fluorescence imaging system. Seventeen patients with lung cancer were enrolled in this study. A 0.3ml sample of solution containing the fluorescent dye ICG (5mg/ml) was injected into subpleural sites near the primary tumor. Fluorescence imaging was used to monitor the flow of ICG-containing lymph from the injection site for 5min. The relationship between the anatomical segment of the primary tumor and the lymphatic flow was assessed. The lymphatic vessels draining from the injection site were revealed by the bright ICG fluorescence in 14 of the patients (82.4%). A direct lymphatic flow to the mediastinum was confirmed in 3 of those 14 (21.4%). These findings confirm the direct flow of lymph to the mediastinum without passage through the hilum pulmonis intraoperatively. These preliminary results may provide a valuable clue for further investigations of the mechanisms underlying skip metastasis.