Dicentric (9;20)(p11;q11) identified by fluorescence in situ hybridization in four pediatric acute lymphoblastic leukemia patients

Four children with acute lymphocytic leukemia (ALL) and a dic(9;20) are described. All four patients were diagnosed with pre-B-cell ALL, and the three for whom information was available were CD1O+. Age at diagnosis ranged from 23 months to 12 years. All patients achieved remission, with two in continuous remission for 2 years 6 months and 3 years, one patient relapsed, dying 3 years 2 months after diagnosis, and one patient was lost to follow- up. These four patients were initially diagnosed as having a deletion of 9p and loss of one chromosome 20. Re-examination of the karyotypes indicated a possible dic(9;20). The dicentric chromosome was verified using dual-color fluorescence in situ hybridization (FISH) with centromeric probes for chromosomes 9 and 20 on interphase nuclei. Three of the four patients had multiple chromosomal abnormalities in addition to the translocation; one was hypodiploid, one was pseudodiploid, and two were hyperdiploid. This dicentric chromosome was recently described in four adult and nine pediatric patients with ALL [8, 9]. All reported patients had CD10+ pre-B-cell ALL, and achieved remission, as was the case for our four pediatric dic(9;20) patients. Two of our three patients for whom follow-up is available are in continuous remission as were two adults and five pediatric patients in the previous reports. These studies confirm the dic(9:20) as a recurring abnormality in ALL. Due to the subtle nature of the translocation, FISH is very useful in confirming the chromosomal abnormality.