Hindawi Publishing Corporation International Journal of Pediatrics Volume 2009, Article ID 674801, 7 pages doi:10.1155/2009/674801 Clinical Study Characterization of Acute Lymphoblastic Leukemia Subtypes in Moroccan Children Fatima Bachir,1 Sanae Bennani,1 Ali Lahjouji,1 Siham Cherkaoui,2 M’hamed Harif,2 Mohamed Khattab,3 Ilham Nassereddine,1 Saadia Zafad,2 and Rajae El Aouad1 1 Laboratoire de cytom´etrie en ﬂux, Institut National d’Hygi`ene, Rabat, Morocco 2 Service d’h´ematologie et oncologie p´ediatrique, Hoˆpital 20 Aouˆt, Casablanca, Morocco 3 Unit´e d’h´emato-oncologie p´ediatrique (UHOP), Hoˆpital d’enfants, Rabat, Morocco Correspondence should be addressed to Fatima Bachir, bachir fatima03@yahoo.fr Received 9 January 2009; Accepted 27 May 2009 Recommended by Eva C. Guinan We present the incidence and the immunologic characteristics of acute lymphoblastic leukemia (ALL) subsets in Moroccan children. We studied 279 unselected patients below the age of 18 years with newly diagnosed ALL. Cases were classiﬁed according to immunophenotype: 216 (77.42%) precursor B-cell phenotype (pB-cell), mature B-cell in 4 (1.43%), and T-cell in 59 (21.15%) cases. The subclassiﬁcation using the CD10 antibody revealed 197 cases pB-ALL CD10+ (91.2%) and 9 cases T-ALL CD10+ (19.2%). The age distribution showed a peak in incidence between 3 and 5 years among the pB-cell ALLs subtype. There was a signiﬁcantly higher frequency of males in the T-ALL subset (M/F ratio: 2.93 : 1) and more females in the T-ALL CD10+ subset when compared with the T-ALL CD10– subset. All tested pB-cell-lineage ALLs expressed CD19, CD79a, and surface CD22, terminal deoxynucleotidyl transferase (TdT) was detectable in 89.9% of cases, and cells in 74.1% of cases express CD34. All tested T-lineage ALL cells have surface CD7 and cytoplasmic CD3 (cCD3) antigens, CD5 was found in 98.2% cases, and 70.5% express TdT. CD1a, surface CD3 (sCD3), and CD4 are detected in more than 80% of cases; this frequency is higher than the 45% generally observed. Myeloid antigens occur more frequently and were expressed in 124 (57.4%) of pB-cell-ALL cases and 20 (33.9%) of T-cell ALL cases. Our results show that the distribution of ALLs in Moroccan children is similar with the general distribution pattern in developed countries except for the high frequency of T-ALL phenotype. The phenotypic proﬁles of our patients are close to those reported in literature for B-lineage ALLs; for the T-cell ALL subgroup, the blast cells express more CD1a, surface CD3, and CD4 while expressing less TdT. The high frequency of CD1a expression resulted in an excess of the common thymocyte subtype. Copyright © 2009 Fatima Bachir et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Introduction Acute lymphoblastic leukemia (ALL) is the most common form of leukemia in children; 75% of cases occur in children under six years of age [1]. The peak in incidence is between the ages of two and ﬁve, and the vast majority of ALL cases (80%–85%) are of precursor B-lineage [1, 2]. Approximately 80% of children with B-ALL appear to be cured [1]. In Morocco, there are two dedicated pediatric oncology units, and compared to that seen in developed countries, treatment is less successful [3, 4]. The survival rate after treatment for ALL children in Morocco is less than 40%, even in specialized centers [3]. In 2003, the St. Jude International Outreach Program became a partner with the two pediatric oncology units to improve the outcome of Moroccan chil- dren with malignancies. In ALL, causes of treatment failure including abandonment of therapy, suboptimal supportive care and lack of uniform treatment guidelines [4, 5] appeared to be the most common. However, there was a possibility that the subtypes of pediatric ALL in Morocco could include an excess of high-risk leukemia subtypes. Since December 2003, the National Hygiene Institute laboratory has become the referral ﬂow cytometry service for acute leukemia for the two pediatric oncology units. The main goal is to have a better survival rate by developing a specialized multidisciplinary care teams and the introduction of a uniform national treatment protocol (MARALLl 2006).