3.1 ︳Clinical characteristics of patients with pre-BLL
Among all the patients with BCP-ALL diagnosed in SCMC from January 2001 to December 2020, nine were identified to carry c-MYC rearrangement. Two of the nine patients were ≥ 10 years old (22%), while the other seven were < 10 years old (78%), with a mean age of 6.8 years (1.5-12.8), close to the average onset age of pre-BLL of 6.1 years7. And there were 4 male children (44%) and 5 female children (56%). Alongside a mature B-cell immunophenotype, patients with BL usually have FAB-L3 morphology, and bulky disease, elevated LDH and UA, at the high risk of tumor lysis8. Cytomorphologic features showed that three of nine patients had FAB-L3 morphology (3/9), four of nine patients had FAB-L2 morphology (4/9), and the other two are not classifiable (2/9). Immunophenotypically, leukemia blasts were uniformly stained for CD10 (9/9), CD19 (9/9) and HLA-DR (9/9). The expression of TdT (6/9), CD34 (1/9), CD20 (3/9) and cμ (1/9) was variable. All the patients lacked the expression of sIgM and negative for kappa/lambda. The white blood cell counts at diagnosis were variable (mean 44,009/mm3; range 710-199,450/mm3). All but one patient had markedly increased serum LDH three times higher than baseline. One of nine patients had bulky disease (1/9). Liver and/or spleen (5/9) and lymph nodes (5/9) were frequently affected. Two patients had central nervous system (CNS) involved (2/9). In addition, one patient had other organs involved, including kidney, pancreas and intestinal wall. The patient with kidney involved was accompanied by renal failure and continuous renal replacement therapy (CRRT) was used at the initial stage of chemotherapy. Tumor lysis syndrome was encountered in induction chemotherapy by two patients, and were corrected soon (Table 1).