The investigators will use the results of the clinical translational trial to determine if sorafenib warrants further clinical study in pediatric LGAs. If the investigators find associations between molecular target expression and response, further studies may be limited to or focus on patients whose tumors have specific molecular features, such as oncogenic BRAF. Sorafenib has also shown promise in combination with classic chemotherapy and can be given together with carboplatin, which is one of the most active agents in LGAs. Therefore, possible synergy between sorafenib and traditional chemotherapy used in the treatment of LGAs, such as carboplatin, could be explored in future clinical trials.