Cytogenetic analysis. (A) GTG-banded representative karyotype at diagnosis showing a 46,XY,-9,+10,del(17)(p11.2) karyotype; abnormal or absent chromosome marked by red arrows. (B) Representative karyotype during relapse showing a 50,XY, +8,+15,del(17)(p11.2), +21,+22 karyotype; abnormal chromosomes marked by red arrows. (C) Partial FISH analysis on chromosomes 12 and 15 demonstrate the cryptic rearrangement t(12;15)(p13q26) and the additional der(15)t(12;15): the 3′ETV6(Cen) signal (green) remains on der(12)t(12;15), and 2 copies of the 5′ETV6 (Tel) signal (red) translocated on 2 copies of der(15)t(12;15).