Fluorescence diagnosis of lymph node metastasis of non-small cell lung cancer has not been reported previously. This study was conducted to evaluate the feasibility of fluorescence detection using 5-aminolevulinic acid and mono-L-aspartyl chlorine e6 for lymph node metastasis in a lung cancer mouse model. Human lung cancer cell line Ma44-3, which forms metastatic lymph nodes in the mediastinum, was injected into the left lungs of 6 severe combined immunodeficiency disease mice. Two weeks after implantation, 2 groups of 3 mice received oral administration of 5-aminolevulinic acid (100 mg/kg) or intraperitoneal administration of mono-L-aspartyl chlorine e6 (5 mg/kg). Both lungs and mediastinal organs were removed en-bloc and illuminated with blue light (405 nm) to evaluate the detectability of lung tumors and metastatic lymph nodes in the mediastinum. These organs were evaluated histopathologically. Clear red fluorescence was observed in the lung tumors of all mice. Metastatic lymph nodes had formed in 5 of 6 mice and were detected by fluorescent detection in all 5 mice even though one of the lymph nodes was invisible macroscopically under white light. In conclusion, fluorescence diagnosis of lymph node metastasis is possible in a mouse model. The successful result with small lymph node metastasis suggests the possibility of clinical application.

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