Detection of acute promyelocytic leukemia (APL) cells intermediately differentiated by all-trans retinoic acid in the cerebrospinal fluid: central nervous system involvement in APL.

We report a patient with acute promyelocytic leukemia (APL) involving the central nervous system. A 55-year-old male was admitted to our hospital with dysarthria and incomplete right hemiplegia. A CT scan of the brain revealed a low density area in the left cerebrum. APL was diagnosed by bone marrow aspiration and chromosomal analysis. The patient received all-trans retinoic acid (ATRA) in combination with chemotherapy. Complete hematological remission (CR) was obtained, and the patient's neurological symptoms improved. However, a cytospin smear of the cerebrospinal fluid after CR showed immature myelocytes ("intermediate cells") that had possibly been derived from leukemic promyelocytes. Comprehensive intrathecal treatment as well as cranial irradiation, caused a further reduction in dysarthria and a complete disappearance of hemiplegia with no atypical cells in the cerebrospinal fluid. The patient has undergone maintenance chemotherapy as an out-patient.