1 ︳INTRODUCTION
The rearrangement of the c-MYC gene is the hallmark of Burkitt leukemia (BL), which is a kind of mature B-cell neoplasms, accounting for about 2% of acute pediatric leukemia. The well characterized immunophenotype for BL is mature B cell phenotype, including CD10, CD19, CD20, CD22, CD79a and sIgM, without the expression of CD34 and terminal deoxynucleotidyl transferase (TdT) 1, 2. Except for BL, c-MYC rearrangement can also occur in other B-cell NHL, such as diffuse large B-cell lymphoma (DLBCL), multiple myeloma (MM) and so on3. Nevertheless, c-MYC rearrangement is also occasionally detected in acute lymphoblastic leukemia (ALL) with an immature B cell immunophenotype of B cell precursor (BCP-ALL). Although the “WHO Classification of Tumors of Hematopoietic and Lymphoid Tissue” has noted these rare cases of BL exhibiting a precursor B-cell phenotype (termed herein “pre-BLL”), the characteristics of it are poorly understood for its rarity4. Because of the overlapping features between BL and pre-BLL, the diagnosis is often delayed and the treatment is controversial, making the clinical management complicated. In order to clarify the clinical and biological characteristics and the treatment outcome of pre-BLL, we report nine patients with pre-BLL in this study.