Immunophenotypic and age patterns of childhood acute lymphoblastic leukemia in Saudi Arabia

Acute lymphoblastic leukemia (ALL) is the most common malignancy of childhood in the West, characteristically showing a peak incidence in children aged between two and five years, and being predominantly of the common ALL (cALL) phenotype. In this article, we examine the hypotheses that ALL is relatively less common among childhood malignancies in Saudi Arabia; that the cALL phenotype is uncommon; that T cell ALL (TALL) is relatively more common. We report that of 163 children with ALL seen at the King Faisal Specialist Hospital and Research Centre, we find that their median age was 5.0 years with a modal value of 3 years, with a range of 4 months to 14 years; that there were 93 cALL patients who were predominantly young (median age 5.0 years). There were 20 (12.3%) patients with TALL, whose median age was 8.5 years, 35 (21.5%) patients who were null cell ALL and whose median age was 6.0 years, 14 (8.6%) patients with B cell ALL whose median age was 9.0 years, and 3 (1.8%) patients with mixed phenotype ALL. We also identify a group of 6 (3.7%) patients whose blasts were CD10 negative and showed B cell differentiation without surface membrane immunoglobulin. We conclude that age and phenotypic characteristics of ALL patients are mainly similar to ALL in the West but that L3 was much more common. A small group of six patients showed unusual B cell phenotype and require further evaluation and analysis.