INCB18424 in Treating Young Patients With Relapsed or Refractory Solid Tumor, Leukemia, or Myeloproliferative Disease

DISEASE CHARACTERISTICS: * Histologically confirmed diagnosis of one of the following: * Relapsed or refractory extracranial solid tumor * Relapsed or refractory leukemia * At least 25% blasts in the bone marrow (M3) with the exception of patients with acute myeloid leukemia (AML), who must have \> 20% blasts in the bone marrow * Relapsed or refractory myeloproliferative neoplasm (MPN) * At original diagnosis or relapse * Current diagnostic criteria for MPNs include polycythemia vera, essential thrombocythemia, juvenile myelomonocytic leukemia, myelofibrosis, and atypical chronic myeloid leukemia * Relapsed or refractory leukemia or MPN that have confirmed JAK mutations and/or positive TSLPR surface staining * Testing for JAK mutations and/or confirmed positive flow cytometry surface staining for the thymic stromal lymphopoietin receptor (TSLPR; encoded by CRLF2); eligibility for part C will be contingent upon patients demonstrating overexpression of CRLF2 by flow cytometric methods measured at either JHU or U. Washington flow laboratories (therefore, pre-enrollment samples need to be sent to one of these laboratories after discussion with Dr. Loh) or if the patient has a CLIA lab documented alteration in JAK1 or JAK2, SH2B3, IL7RA, or another gene that would predict sensitivity to JAK inhibition. * Measurable or evaluable disease (for patients with solid tumors) * Current disease state is one for which there is no known curative therapy or therap…