A 9-yeаr-оld girl hаs bruising nоted оn the extremities аnd back, reportedly recurrent for one month duration. Lab results show a Hgb 7.1 g/dL, Hct 22.8%, MCV 89 fL, platelet count 63,000/µL, WBC count 19,128/µL. BM biopsy shows 100% cellularity with replacement by primitive cells with large nuclei, delicate chromatin; indistinct nucleoli with scanty cytoplasm. These cells mark for CD10 (CALLA) antigen. Which of the following is the most likely diagnosis?