A leukemia cerebrospinal fluid test with 20 nucleated cells indicates that there may be a CNS leukemia condition, but a specific determination still needs to be made based on the type and maturity of that nucleated cell. 1. If the nucleated cells are leukocytes, and all are mature nucleated cells, then it can be considered that there may be CNS lesions, such as: purulent meningitis, tuberculous meningitis, parasitic infections and so on. 2. If the cerebrospinal fluid nucleated cells show naïve nucleated cells, then it is considered that the leukemia is progressing to the stage of CNS leukemia, and the relative treatment will change. Sequential lumbar puncture and intrathecal injection of chemotherapeutic agents, including methotrexate, cytarabine, and dexamethasone, may be used to target the disease. If there is an increase in nucleated cells in the cerebrospinal fluid of leukemia patients, please be sure to follow the doctor’s instructions for standardized and timely examination and diagnosis and treatment.