Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 8 2 2009 06 15 99 106 Ramyar Asghar Department of Hematology and Oncology of Children's Medical Center, Tehran University of Medical Sci Shafiei Masoud Department of Hematology and Oncology of Children's Medical Center, Tehran University of Medical Sci Rezaei Nima Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Ir Asgarian-Omran Hossein Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Ir Abdar Esfahani Shadi Department of Hematology and Oncology of Children's Medical Center, Tehran University of Medical Sci Moazzami Kasra of Hematology and Oncology of Children's Medical Center, Tehran University of Medical Sciences, Tehr Sarafnejad Abdolfattah Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Ir Aghamohammadi Asghar Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Ir 2015 10 01 Acute lymphoblastic leukemia (ALL) is a malignant disorder of lymphoid precursor cells, which could be classified according to morphological and cytochemical methods as well as immunophenotyping. Twenty patients with ALL, who had been referred to the Children's Medical Center Hospital, during the year 2007, were enrolled in this study in order to evaluate the morphologic and immunophenotypic profile of these patients. Cytologic analysis of blood and bone marrow samples revealed that the frequency of ALL-L1 was 70%, followed by ALL-L2 and ALL-L3. The onset age of the patients with ALL-L1 was significantly lower than the patients with L2/L3. Severe anemia was significantly detected more in L1 group. Flow cytometic study of bone marrow showed that 10 cases had Pre-B1 ALL and 7 cases had Pre-B2 ALL, while three cases had Pro-B ALL. Comparisons of the characteristics and clinical manifestations among these groups did not show any appreciable difference. There were an increase percentage of CD20+ cells and a decrease CD10+ cells in pre-B2 group in comparison with pre-B1 group. Fifteen patients were in standard risk and five were in high risk. Although standard risk patients were more common in the group of pre-B1, this was not significant. Our results confirm the previous reports indicating heterogeneity of ALL. Immunophenotyping is not the only diagnostic test of importance, while morphological assessment still can be used in the diagnosis and classification of the disease. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/241 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/241/241