Moving from these findings we tested whether FCM detection of CCR2-expressing CD34+ cells could represent an accurate diagnostic tool for the differential diagnosis of MPN subtypes with different degrees of bone marrow fibrosis, with a focus on compelling clinical scenarios, i.e. prePMF vs “true” ET and overtPMF vs prePMF. The gene discussed is CCR2; the disease is myeloproliferative neoplasm.