The European Cooperative Study Group for Paediatric Rare Tumors (EXPeRT group): A Model for Collaborative Research and Clinical Care in Very Rare Paediatric Tumours

Paediatric cancers, though all considered rare, have benefited substantially from international collaborative protocols. However, very rare tumours (VRT) in children and adolescents, defined by an annual incidence < 2/1,000,000, pose significant challenges. These malignancies represent more than 50 different histotypes and collectively account for approximately 11% of all paediatric cancers. The European Cooperative Study Group for Paediatric Rare Tumours (EXPeRT) was established in 2008 to address the unique challenges posed by these rare malignancies through collaborative research, multidisciplinary clinical expertise, and international cooperation. Over the past 15 years, EXPeRT has established a comprehensive framework integrating expert clinical consultation, harmonized consensus guideline development, retro- and prospective collaborative research, and strategic international partnerships. This article provides a comprehensive overview of EXPeRT's structure, scientific contributions, and vision for future cross-disciplinary and cross-border initiatives aimed at improving outcomes for children and adolescents with very rare tumours.