DICENTRIC (9-20)(P11-Q11) IDENTIFIED BY FLUORESCENCE IN-SITU HYBRIDIZATION IN 4 PEDIATRIC ACUTE LYMPHOBLASTIC-LEUKEMIA PATIENTS

Four children with acute lymphocytic leukemia (ALL) and a dic(9;20) ar e described. All four patients were diagnosed with pre-B-cell ALL, and the three for whom information was available were CD10+. Age at diagn osis ranged from 23 months to 12 years. All patients achieved remissio n, 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 diag nosed as having a deletion of 9p and loss of one chromosome 20. Re-exa mination of the karyotypes indicated a possible dic(9;20). The dicentr ic chromosome was verified using dual-color fluorescence in situ hybri dization (FISH) with centromeric probes for chromosomes 9 and 20 on in terphase nuclei. Three of the four patients had multiple chromosomal a bnormalities in addition to the translocation; one was hypodiploid, on e was pseudodiploid, and two were hyperdiploid. This dicentric chromos ome was recently described in four adult and nine pediatric patients w ith ALL [8, 9]. All reported patients had CD10+ pre-B-cell ALL, and ac hieved remission, as was the case for our four pediatric dic(9;20) pat ients. Two of our three patients for whom follow-up is available are i n continuous remission as were two adults and five pediatric patients in the previous reports. These studies confirm the dic(9;20) as a recu rring abnormality in ALL. Due to the subtle nature of the translocatio n, FISH is very useful in confirming the chromosomal abnormality. (C) Elsevier Science Inc,, 1996