Schneider, Dominik T.; Ferrari, Andrea; Orbach, Daniel; Virgone, Calogero; Reguerre, Yves; Godzinski, Jan; Bien, Ewa; Roganović, Jelena; Farinha, Nuno Reis; Ben-Ami, Tal; Stachowicz-Stencel, Teresa; Blessing, Tabea; Redlich, Antje; Pourtsidis, Apostolos; Schultz, Kris Ann P.; Brecht, Ines B.; Bisogno, Gianni: A virtual consultation system for very rare tumors in children and adolescents – an initiative of the European Cooperative Study Group in Rare Tumors in Children (EXPeRT)