Complex chromosome 9, 20, and 22 rearrangements in acute lymphoblastic leukemia with duplication of BCR and ABL sequences

Cytogenetic analysis was performed on bone marrow cells from a 28-year-old woman who was diagnosed with acute lymphoblastic leukemia (ALL). Her karyot ype was: 46,XX,t(9;22)(q34;q11)[6]/47,XX,+8,t(9;22)(q34;q11)[4]/47,XX,+8,t( 9;22)(q34;q11),del(20)(q11[4]/47,XX,t(9;22)(q34;q11),del(20)(q11)[7]/45,XX, der(9)t/9;22)(q34;q11),-20,-22,+mar1[8]/45,XX,der(9)t(9;22)(q34;q11),-20,-2 2,+mar2[3]. Both marker chromosomes are dicentric and have the same size an d banding pattern but different primary constrictions. Fluorescence in situ hybridization (FISH) demonstrated that both markers were derived from chro mosomes 9, 20, and 22. FISH with the bcr/abl probe showed fusion of the BCR gene with the ABL gene; however, this fusion signal was present in duplica te on both marker chromosomes. To our knowledge, duplication of the BCR/ABL fusion signal on a single chromosome arm has not been reported before, exc ept for the extensive amplification of BCR/ABL fusion signals in the leukem ic cell line K-562. These data demonstrate that the marker chromosomes are the result of complex genomic rearrangements. At the molecular level, the B CR/ABL fusion gene encodes the p190 fusion protein. Similar findings have n ever been observed in any case of ALL. (C) Elsevier Science Inc., 1999. All rights reserved.