Clinical and genetic features of pediatric acute lymphoblastic leukemia in Down syndrome in the Nordic countries

Table 2 Genetic features of the DS-ALL and the non-DS-ALL patients

Features	DS-ALL (%)	non-DS-ALL (%)	P value^a
Karyotype
Abnormal	57 (60)	2581 (79)	<0.0001
Normal	38 (40)	702 (21)
Modal number ^b
Hypodiploidy	1 (1)	211 (6)	<0.0001
Pseudodiploidy	37 (39)	940 (29)
Hyperdiploidy	17 (18)	329 (10)
High hyperdiploidy	2 (2)	1075 (33)
>67 chromosomes	0 (0)	26 (1)
Normal karyotype	38 (40)	702 (21)
*TCF3* - *PBX1* ^c
Yes	1 (2.6)	70 (4.2)	1.00
No	37 (97)	1592 (96)
*BCR* - *ABL1* ^c
Yes	1 (2.1)	73 (3.7)	1.00
No	46 (98)	1923 (96)
*MLL* rearrangement ^c
Yes	0 (0)	122 (7.6)	0.07
No	41 (100)	1487 (92)
*ETV6* - *RUNX1* ^c
Yes	8 (15)	568 (25)	0.11
No	46 (85)	1719 (75)
t(8;14)(q11;q32)
Yes	2 (2.1)	3 (0.09)	NA
No	93 (98)	3280 (99.9)
iAMP21 ^d
Yes	0 (0)	6 (1.1)	NA
No	12 (100)	558 (98.9)

DS-ALL, Down syndrome-related acute lymphoblastic leukemia; iAMP21, intrachromosomal amplification of chromosome 21; NA, not analyzed due to too few cases.
^aChi square test. Significant P values in bold type.
^bHypodiploidy was defined as <47 in DS and <46 in non-DS; pseudodiploidy as 47 in DS and 46 in non-DS; hyperdiploidy as 48–50 in DS and 47–50 in non-DS; and high hyperdiploidy as 51–67 chromosomes in both groups.
^cBased only on informative cases, i.e., on which targeted molecular genetic or FISH analyses of these rearrangements had been performed.
^dBased only on informative cases, i.e., on cases treated according to the ALL-2008 protocol and hence screened for iAMP21.

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