BACKGROUND: CD56 which is considered as a marker of natural killer cells is also expressed in some cases of acute myelogenous leukemia (AML) and is involved in cell adhesion mediating extramedullary leukemic infiltration. CD7/CD56 coexpression has been suggested to be a distinct biological and clinical entity of AML. PATIENT: This is a report of a 53-year-old woman who developed CD7/CD56-positive AML with primary manifestation as intracranial tumor. The patient reported of neurological impairment (impairment of visus and occurrence of double pictures). Cranial computed tomography showed an intracranial tumor, and histological examination exhibited myeloid blast cells. Peripheral leukocyte count at admission was within the normal range (5,32 Gpt/l), and percentage frequency of blasts in the blood smears was 54%. Cytological bone marrow examination showed diffuse infiltration by the same myeloid blast cells. The immunophenotype was CD7/CD13/CD33/CD38/CD56/ HLA-DR-positive. The blast cells were myeloperoxidase-positive but lactoferrin-negative. Thus, diagnosis of acute myeloid leukemia (M2 FAB) was established. Treatment consists of chemotherapy (Ara-C and anthracycline) and local radiation of the intracranial tumor. After treatment patient achieved a complete remission. CONCLUSION: With regard to the literature CD7/CD56-positive AML have a high incidence of central nervous system involvement which should be kept in mind and may be associated to CD56 expression. Copyright 2000 S. Karger GmbH, Freiburg