Figure 2. Fluorescence in situ hybridization (FISH) analyses of pediatric leukemia. (A) Interphase FISH at initial diagnosis of AML with the KMT2A break-apart probe showing a normal (yellow) and split (separated red and green) signals of the probe in 3 nuclei. (B) FISH analysis at initial diagnosis of AML with the KMT2A-MLLT3 translocation dual fusion probe on metaphase spreads showing a normal green signal on chromosome 11, corresponding to KMT2A, a normal red signal on chromosome 9, corresponding to MLLT3, and two yellow fusion signals on der(11) and der(9) corresponding to the KMT2A-MLLT3 and MLLT3-KMT2A fusion genes, respectively. (C) Interphase FISH at initial diagnosis of AML on two nuclei using the KMT2A-MLLT3 translocation dual fusion probe showing a normal green signal, corresponding to KMT2A, a normal red signal, corresponding to MLLT3, and two yellow fusion signals corresponding to the KMT2A-MLLT3 and MLLT3-KMT2A fusion genes. (D) Interphase FISH with the break-apart KMT2A probe on the sample obtained 300 days after diagnosis showing deletion of the distal part of the KMT2A probe (lack of red signal) in two nuclei and two normal (yellow) KMT2A signals in one nucleus. (E) FISH analysis with the break-apart KMT2A probe on metaphase spread from the sample obtained 1,198 days after diagnosis, when a t(14;19)(q32;q13) was seen by karyotyping and the patient had developed ALL. The distal part (red signal) of the probe is absent in one of the two copies of chromosome 11. (F) Interphase FISH with the IGH break-apart probe on the sample obtained 1,198 days after diagnosis, when a t(14;19)(q32;q13) was seen by karyotyping and the patient had developed ALL. A normal (yellow) and split (separated red and green) signals of the probe are shown in 2 nuclei. (G) FISH analysis with the IGH break-apart probe on a metaphase spread from the sample obtained 1,198 days after diagnosis, when a t(14;19)(q32;q13) was seen by karyotyping and the patient had developed ALL. A normal (yellow) signal on chromosome 14 together with separate red, on der(14), and green, on der(19), probe signals are shown.