Cytogenetic abnormalities in childhood acute myeloid leukaemia: a Nordic series comprising all children enrolled in the NOPHO‐93‐AML trial between 1993 and 2001

Abstract

Summary. Between 1993 and 2001, 318 children were diagnosed with acute myeloid leukaemia (AML) in the Nordic countries. The patient group comprised 237 children < 15 years of age with de novo AML, 42 children < 15 years with Down syndrome (DS) and de novo AML, 18 adolescents 15–18 years of age with de novo AML, and 21 children < 15 years with treatment‐related AML (t‐AML). The first group was all‐inclusive, yielding an annual childhood de novo AML incidence of 0·7/100 000. Cytogenetic analyses were successful in 288 cases (91%), and clonal chromosomal abnormalities were detected in 211 (73%). The distribution of ploidy levels were pseudodiploidy (55%), hyperdiploidy (34%) and hypodiploidy (11%). The most common aberrations (> 2%) were + 8 (23%) (as a sole change in 6·2%), 11q23‐translocations, including cryptic MLL rearrangements (22%) [t(9;11)(p21–22;q23) in 11%], t(8;21)(q22;q22) (9·0%), inv(16)(p13q22) (6·2%), −7/7q– (5·2%), and t(15;17)(q22;q12) (3·8%). Except for +8, these abnormalities were rare in group 2; only one DS patient had a t(8;21) and none had 11q23‐translocations, t(15;17) or inv(16). In the t‐AML group, three cases displayed 11q23‐rearrangements, all t(9;11); and there were no t(8;21), t(15;17) or inv(16). Overall, the observed frequencies of t(8;21) and t(15;17) were lower, and frequencies of trisomy 8 and 11q23‐translocations higher, than in previous studies. Furthermore, seven abnormalities that were previously reported as only single AML cases were also seen, meaning that der(4)t(4;11)(q26–27;q23), der(6)t(1;6)(q24–25;q27), der(7)t(7;11)(p22;q13), inv(8)(p23q11–12), t(11;17)(p15;q21), der(16)t(10;16)(q22;p13) and der(22)t(1;22)(q21;q13) are now classified as recurrent abnormalities in AML. In addition, 37 novel aberrations were observed, 11 of which were sole anomalies.