A 7-year-old boy has complained of a severe headache for the past week. On physical examination, there is tenderness on palpation of long bones, hepatosplenomegaly, and generalized lymphadenopathy. Petechial hemorrhages are present on the skin. Laboratory studies show hemoglobin, 8.8 g/dL; hematocrit, 26.5%; platelet count, 34,700/mm3; and WBC count, 14,800/mm3. A bone marrow biopsy specimen shows 100% cellularity, with almost complete replacement by a population of large cells with scant cytoplasm lacking granules, delicate nuclear chromatin, and rare nucleoli. His oncologist is confident that chemotherapy will induce a complete remission. Which of the following combinations of phenotypic and karyotypic markers is most likely to be present in marrow cells from this boy?

These markers strongly favor a very good prognosis for acute lymphoblastic leukemia (ALL), the most common malignancy in children: early precursor-B-cell type, hyperdiploidy, and patient age between 2 and 10 years, chromosomal trisomy, and t (12;21). Marrow infiltration by the leukemic cells leads to pancytopenia. Poor prognostic markers for acute lymphoblastic leukemia/lymphoma are T-cell phenotype, patient age younger than 2 years, WBC count >100,000, presence of t (9;22) MLL gene mutations, and presentation in adolescence and adulthood. In most T-cell ALL cases in adolescents, a mediastinal mass arises in the thymus, and lymphoid infiltrates appear in tissues of the mononuclear phagocyte system. The success of a treatment plan is also aided by a caring and supportive family.