RecruitingClinical Epidemiology in Contemporary Patients With Myelofibrosis.Multicenter retrospective and prospective European observational study. At each site, all consecutive patients with a 2016- or 2022 World Health Organization (WHO) confirmed diagnosis of myelofibrosis (MF) established from 01/01/2018 to 31/12/2027 will be enrolled into the study. Yearly follow-up updates will be scheduled until the end of data collection on 31/12/2028 or until the last available patient visit, whichever comes first. At least 1 year of follow-up will be ensured from the last patient enrolled.