[Leukemia]

Leukemia is derived from hematopoietic stem/progenitor cells that have acquired genetic abnormalities, leading to malignant transformation. The basis of therapyfor leukemia is a combination of anti-cancer drugs based on risk stratification. The overall 5-year survival rate in leukemia patients of all ages is still 40%, although it has improved in pediatric patients. Leuke- mia itself is a heterogeneous disease that includes various entities/subtypes with different pathogenic gene aberrations. Selection of the treatment strategylargelydepends on risk stratification, and this in turn is mainlybased on specific recurrent chromosome aberrations. However, in acute myeloid leukemia(AML), a significant proportion of patients present with a normal karyotype according to conventional cytogenetic analysis and are classified into an intermediate-risk group, which actuallyconsists of various subtypes with different prognoses. In addition, leukemic cells usuallyharbor one or more driver mutations among their various genetic aberrations, and these driver mutations could affect prognosis. The discoveryof additional mutations in genes such as NPM1, CEBPA and FLT3, which are frequent in AML patients with a normal karyotype, have improved the precision of risk stratification in AML. In this regard, array-based gene expression analysis and whole exome/ transcriptome sequencing could be useful tools for identifying the whole spectrum of genetic aberrations, or for compiling a complete list of mutated genes within leukemic cells. Genetic profiling information obtained using these newlydeveloped methods could provide more accurate information for molecular subtyping and risk stratification in leukemia.