The investigators aim to describe the patient and tumor characteristics, treatments, and outcomes of children and adolescents diagnosed with primary gastrointestinal malignancies, and to analyze these data for trends over time. In addition, the investigators want to explore independent prognostic factors for overall survival. Finally, the investigators want to describe subsequent primary malignancies diagnosed among patients from the study cohort, as well as to calculate their risk of developing a second primary cancer relative to the general population. Data on children (aged 0-17 years at diagnosis) and young people aged 18-24 years at diagnosis are analyzed separately. Special focus is laid on patients with primary carcinomas of the gastrointestinal tract; particularly colorectal carcinoma.
