ABSTRACT
Acute Lymphoblastic Leukemia [ALL] is a malignancy of immature lymphoid cells, which comprises the highest incidence of acute leukemia in children. Many attempts were made to morphologically classify ALL. Most of these were unsuccessful either because of its technical difficulties, or because it lakes the clinical significance. Hence the immuno classification is more specific and shows that leukemia may occur in different stages of lymphoid maturation. T-ALL is a neoplasm of lymphoblasts committed to the T cell linage and observed in 20% of the children who suffer from ALL. Also it is more common in young adults, and in males rather than females. It manifests by low count of leukocytes and sometimes by existence of a mass. T-ALL is classified to different stages according to the number of antigens and their expression. Immunophenotyping was achieved for 50 samples collected from children visiting children hospital in Damascus with suspected ALL. 24% of ALL was classified as T-ALL. 83.3% of them were males and 16.7% were females. Occurrence of ALL was 41.7% in the group of 6 - 9 years of age. Also it was found that 58.3%, 25%, 16.7% of the studied samples represented as late T-ALL, Middle T-ALL, and Early T-ALL respectively