Molecular diagnosis of lymphoblastic leukemia

The mixed lineage leukemia (MLL) gene at chromosome band 11q23 is commonly involved in reciprocal translocations that is detected in acute leukemia. The MLL gene, commonly known as mixed lineage leukemia or myeloid lymphoid leukemia, has been independently identified and cloned from the 11q23 breakpoint of acute leukemia. We describe a patient with acute lymphoblastic leukemia whose cells had shown reciprocal translocation between short arm (p21) of chromosome 2 and long arm (q23) of chromosome number 11 [t(2;11) (p21;q23)] by cytogenetic analysis. Fluorescence in situ hybridization analysis (FISH) was also performed for reconfirmation with a probe for MLL which showed split signals, hybridizing to both the derivative 2 and 11 chromosomes. Our study confirmed FISH as the most suitable assay for detecting MLL rearrangements because of its sensitivity and speed. It recommended that FISH should be used as complementary to conventional cytogenetic analysis. In conclusion, evaluation of the t(2;11)(p21;q23) was done by molecular clarification and flow cytometry.