Abstract OBJECTIVE: To investigate the biological characteristics of childhood T-lineage acute lymphoblastic leukemia (T-ALL) and their clinical significance. METHODS: Immunophenotyping was performed by three-color flow cytometry analysis using CD45 /SSC gating in 23 children with newly diagnosed T-ALL. Meanwhile cytogenetic analysis was performed. RESULTS: CD3+ expression of T-lineage antigens was apparently higher than CD7+ and CD5+ expression. CD19+ expression of B-lineage antigens was apparently higher than CD22+, CD10+ and CD20+ expression. Myeloid antigen was expressed in 4 cases (17%). CD34+ and HLA-DR+ were observed in 4 cases (17%) and 5 cases (22%), respectively. cCD3+ and cCD79+ were expressed in 23 cases (100%) and 22 cases (96%), respectively. The chromosome detection in 8 cases with T-ALL showed hyperdiploid or Ph+ chromosome (one case each). The fusion gene detection in 5 cases showed MLL rearrangements in two cases and positive SIL/TAL1 fusion gene in one case. CD3 expression was related with the complete remission rate. CONCLUSIONS: Immunophenotyping is an important tool for diagnosis of T-ALL. However, the immunophenotype of T-ALL is heterogeneous. So, immunophenotyping along with cytogenetic and molecular genetic analysis is needed in the treatment and prognosis evaluation of T-ALL.［Chin J Contemp Pediatr, 2010, 12 (8):605-608］
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