Cytokeratin is CYFRA21-1, and high CYFRA21-1 after lung cancer surgery indicates further deterioration of lung cancer. CYFRA21-1 is an acidic peptide, which belongs to one of the tumor markers and is distributed in alveolar epithelium. According to the results of this test, it can be used to assist in determining whether there is lung cancer, and after surgery, CYFRA21-1 can also be used to assess whether the condition has progressed, and the higher the value of CYFRA21-1, the more serious the condition is at present. The higher CYFRA21-1 value, the more serious the current condition is. Higher CYFRA21-1 value after lung cancer surgery indicates that the current condition has progressed, and there may be recurrence or metastasis, such as liver metastasis, bone metastasis, lymph node metastasis, and so on. If CYFRA21-1 is found to be high after lung cancer surgery, one should consult a doctor as soon as possible and take radiotherapy, targeted drugs or immune drugs under the doctor’s guidance to slow down the progress of the disease, so as to avoid delaying the treatment.