CHARACTERIZATION OF ACUTE-LEUKEMIA WITH T(4-12)

Acute leukemia with t(4;12)(q11-13;p12-13) is rare but has unique char acteristics. The incidence of t(4;12) in acute leukemias was about 0.6 % in our laboratory. Twelve patients with acute leukemia with t(4;12) have been reported until now. They included eight acute myeloid (AML: MO 2, M1 3, M2 1, M4 1, and M7 1), three acute lymphoblastic (ALL: L1) and one acute unclassified leukemia (AUL). There were some difference s between adults and children with t(4;12). The eight adult patients i ncluded seven with AML and one with AUL, two of whom had a history of exposure to mutagenic agents and/or genotoxic therapy. Three patients had the CD7(+)HLA-DR(+)CD13(+)CD34(+)c-kit(+) phenotype, suggesting th at the leukemic cells were of stem cell origin. Four children expresse d the B lymphoid phenotype (HLA-DR(+)CD10(+)CD19(+)) although one had myeloperoxidase positivity. It was difficult for adult patients to ach ieve complete remission with the usual therapy regimen, whereas childr en with t(4;12) seemed to be easier to treat. Rearrangement of the TEL gene located on the short arm of chromosome 12 (12p13), was investiga ted in two adult patients. FISH analysis using the YAC probe that cove rs the TEL gene region, revealed split signals in these patients, sugg esting a break inside or near the TEL gene. The t(4;12) abnormality is associated with unique characteristics of acute leukemia namely stem cell or secondary AML in adults, and B lymphoid leukemia in children.