Study for Epidemiology and Characterization of Myelodysplastic Syndromes (MDS) and Juvenile Myelomonocytic Leucemia (JMML) in Childhood

The aim of the study is to improve the accuracy of diagnosis for children and adolescents with MDS by a standardized review of morphology and standardized cytogenetic and molecular analysis. The primary objectives of the study are: * To evaluate the frequency of the different subtypes of MDS in childhood and adolescence by a standardized diagnostic approach * To evaluate the frequency of cytogenetic and molecular abnormalities: Specifically using array-CGH to evaluate the frequency of subtle chromosomal imbalances, i.e. gains and losses of defined chromosomal regions, and amplifications. Specifically using mFISH to identify unknown chromosomal aberrations, particularly subtle translocations involving new candidate genes, and to better define chromosomal breakpoints. The secondary objectives of the study are: * To assess survival for children and adolescents with MDS and JMML * To evaluate relapse rate, morbidity and mortality in children with MDS and JMML treated by HSCT