Variant philadelphia translocations in chronic myeloid leukemia: correlation with cancer breakpoints, fragile sites and oncogenes

Abstract

Four cases of variant Philadelphia (Ph 1) translocations were found in 72 patients (5.5%) with Ph 1-positive chronic myeloid leukemia (CML). One previously unreported case was a simple variant translocation, namely, 46,XY,t(11; 17) (q13;p13),t(17;22) (q25;q22); 46,XY,t(1;21)(q32;q11),t(11;17)(q13;p13), t(17;22)(q25;q11). Complex variant translocations were observed in three cases, namely, 46,XY,t(5;9;22)(q31;q34;q11),46,XX,t(8;9 ;22)(q22;q34;q11) and 46,XX,t(9;15;22) (q34;q15;q11). The chromosomal breakpoints in the cases of variant Ph 1 translocations were the following: 1q32, 5q31, 8q22, 11q13, 15q15, 17p13, 17q25 and 21q11. Eight of the eight (100%) breakpoints were located in Giemsa-negative bands. Furthermore, seven of the eight (87%) variant Ph 1 breakpoints correspond to the breakpoints present in consistent cancer arrangements. Three of the eight (38%) correspond to fragile sites and four of the eight (50%) correspond to oncogenes.