This project aims to refine the prognosis and increase the effectiveness of the treatment of neuroblastoma, a very aggressive cancer in children. The first part of the project focuses on the development and validation of a prognostic signature tumor (microRNA) based on a simple blood test in patients. This non-invasive method should be used to identify patients who do not benefit from current therapeutic approaches. Thus these children have not suffered serious useless treatments. They can thus be considered for clinical trials of new molecular therapies.