Chromosome negativity is normal in chronic leukemia. Chromosome negativity can be used to determine the efficacy of treatment and prognosis of lentigo leukemia. One of the characteristics of lentigo leukemia is Philadelphia chromosome positivity. When patients with lentigo leukemia return to the clinic after treatment, in addition to bone marrow aspiration and routine blood tests, chromosome tests can also be performed. After treatment (imatinib), the Philadelphia chromosome chromosome becomes negative, indicating that the treatment effect is relatively good, and long-term stable survival can be obtained. If the chromosomes reappear positive, it suggests that the leukemia may relapse. Treatment of chronic granulocytic leukemia with tyrosine kinase inhibitors can achieve chromosome and fusion gene turnover, and thus achieve a state of cure, but even after cure, the disease has the possibility of relapse, and should be under the guidance of a physician to receive treatment and regular review.