We are analyzing single cell RNA Seq data from pediatric brain tumor patients at primary diagnosis and at recurrence in a clinical study we are conducting at Uppsala University Hospital and in collaboration with Barntumörbanken, Karolinska Hospital. The data is pseudonymised but can be coupled to individuals needs and need to be handled as sensitive data. The study is conducted in order to follow molecular changes from primary diagnosis to recurrence with the intention to find better understanding of the relapse process but also to find new clues for better treatment of these devastating childhood brain tumors.