An 18-year-old male presents with fever for 2 months. Physical examination reveals lymphadenopathy in the neck and axilla, liver palpable 2 cm below the costal margin, spleen palpable 3 cm below the costal margin, and petechiae. Lab results: hemoglobin 76 g/L, WBC count 7.2×10<sup>9</sup>/L, platelets 65×10<sup>9</sup>/L. Symptoms resolved after treatment with the VDP regimen (vincristine, daunorubicin, prednisone). The most likely diagnosis is: