The classic myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), myelofibrosis (MF), and essential thrombocythemia (ET), heterogeneous disorders of the hematopoietic system collectively known as Philadelphia chromosome-negative (Ph-) MPNs. This activity will assist clinicians in improving diagnosis for patients with MF. Learners will gain a greater understanding of pathophysiologic mechanisms of MF.