Table 1. Clinical and biological characteristics of 59 Norwegian AML patients included in the study.

Age (median, range)	62.5 years (range 27-88)
Number of patients with: Secondary AML AML relapse de novo AML	15 14 30
FAB classification (number of patients) M0/M1 M2 M4/M5	24 12 23
Expression of CD34 (percentage of patients)*	36%
Cytogenetic abnormalities (patient numbers)* Normal Good Intermediate Adverse Not determined	23 4 7 11 12
Frequency of Flt3- internal tandem duplication (ITD)	36%
Frequency of NPM1 mutations	44%

^*CD34 positivity was defined as at least 20% of the cells staining positive for the CD34 stem cell marker. Cytogenetic abnormalities were classified according to the MRC guidelines. Cytogenetic analysis was not available for 12 patients; this was due to either no mitoses to analyze, death or start of chemotherapy in elderly patients due to critical illness, hyperleukocytosis or other severe complications before sampling for cytogenetic analysis was possible. Cytogenetic analyses were only performed on freshly isolated cells and never on cryopreserved cells [13].