This study proposes to treat patients with the combination of erlotinib and temozolomide. Patients with relapsed, recurrent, refractory, or high risk malignancies whose tumors possess a non-synonymous mutation in EGFR, ERBB2, or JAK2V617F (JAK2) will be eligible for the study. Very few phase 2 clinical trials have been performed in pediatrics using targeted agents in combination with conventional chemotherapy agents. Furthermore, since some combinations such as the combination of this study (erlotinib and temozolomide) have shown additive/synergistic effects in preclinical studies, therapy selecting for those patients who possess mutations targeted by the TKI of the study, may unveil activity that has not been previously observed. Thus, the investigators hope to determine whether the addition of additive/synergistic chemotherapy will increase efficacy of target agent and/or increase tumor susceptibility to targeted agent resulting in increased anti-tumor activity.