Nivolumab in Treating Patients With Primary Myelofibrosis, Post-Essential Thrombocythemia Myelofibrosis, or Post-Polycythemia Vera Myelofibrosis

Nivolumab in Treating Patients With Primary Myelofibrosis, Post-Essential Thrombocythemia Myelofibrosis, or Post-Polycythemia Vera Myelofibrosis