Neuroblastoma serves as a paradigm for utilising tumour genomic data for determining patient prognosis and treatment allocation. However, before the establishment of the International Neuroblastoma Risk Group (INRG) Task Force in 2004, international consensus on markers, methodology, and data interpretation did not exist, compromising the reliability of decisive genetic markers and inhibiting translational research efforts. The objectives of the INRG Biology Committee were to identify highly prognostic genetic aberrations to be included in the new INRG risk classification schema and to develop precise definitions, decisive biomarkers, and technique standardisation. The review of the INRG database (n ¼ 8800 patients) by the INRG Task Force finally enabled the identification of the most significant neuroblastoma biomarkers. In addition, the Biology Committee compared the standard operating procedures of different cooperative groups to arrive at international consensus for methodology, nomenclature, and future directions. Consensus was reached to include MYCN status, 11q23 allelic status, and ploidy in the INRG classification system on the basis of an evidence-based review of the INRG database. Standardised operating procedures for analysing these genetic factors were adopted, and criteria for proper nomenclature were developed. Neuroblastoma treatment planning is highly dependant on tumour cell genomic features, and it is likely that a comprehensive panel of DNA-based biomarkers will be used in future risk assignment algorithms applying genome-wide techniques. Consensus on methodology and interpretation is essential for uniform INRG classification and will greatly facilitate international and cooperative clinical and translational research studies.

Neuroblastoma (NB) is the most frequent solid tumour in early childhood. NBs are extremely heterogeneous in terms of their biological characteristics and the clinical behaviour which ranges from lethal disease to spontaneous regression and/or differentiation. Genetically, the heterogeneity of these tumours is reflected mainly by differences in the DNA content, presence of chromosome lp deletions and amplification of the proto-oncogene N-myc. Up to now, only the prognostic impact of N-myc amplification, based on a large series of analysed tumour samples, was established and is now used as the discriminating factor for treatment stratification in a newly developed European protocol. The influence of other genetic aberrations, i.e. dellp36, t(l;17), ploidy and expression of certain proteins, such as nerve growth factor (NGF) receptor proteins and CD44, on the biological behaviour were studied only in a limited number of cases. We will review the literature and outline our own observations dealing with the peculiar phenomena observed in some NBs, i. e. spontaneous regression and/or maturation.

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