The SIOPEN Circulating RNA Committee (CRC) has designed and validated an RTqPCR test, detecting adrenergic mRNAs in blood and bone marrow aspirates, allowing identification of children with high-risk neuroblastoma disease. Recently, it became clear that neuroblastoma contains cells with an adrenergic or mesenchymal signature, and that the number of mesenchymal cells increases in post-treatment and relapse tumours. In addition, it has become clear that non-coding RNA transcripts have an important role in neuroblastomas development, and might be used to detect residual neuroblastomas cells. Therefore, in this project we will investigate the hypothesis that a combination of mesenchymal and adrenergic neuroblastoma RNAs – coding and non-coding - will most reliably detect clinically relevant disease.