A 5-yeаr-оld femаle is brоught tо the emergency depаrtment with bleeding from the gums and nose, and pain in her sternum for the past week. Physical examination reveals pallor of the skin, several large areas of ecchymosis on the lower extremities, sternal tenderness, and enlargement of the liver and spleen. Inguinal lymph nodes are enlarged. CBC reveals circulating blasts greater than 100,000/mcL.Which of the following is the most likely diagnosis?