The level of irisin in the N2 group (mean 2.8 ± 0.28) was significantly higher than in the group without lymph node metastases (N0, mean 2.2 ± 0.12) and in the group with metastases to hilar and intrapulmonary lymph nodes (N1, 1.7 ± 0.20) (Mann-Whitney U, p = 0.0124; p = 0.011, respectively). The gene discussed is FNDC5; the disease is metastatic malignant neoplasm in the lymph nodes.