Ring sideroblasts in chronic phase of polycythemia vera identifies a subset of patients with an increased risk of progression to blast phase

Blast phase of PV is often associated with a complex karyotype (CK) and bilineage dysplasia. We hypothesized that BM morphologic abnormalities detected in the Chronic phase (CP) can identify patients with an increased risk of developing blast phase (BP). We also compared cases of BP PV to a group of acute myeloid leukemia cases with JAK2 mutation (AML-JAK2mut). We collected morphological, cytogenetics (CG), and molecular information at the time of diagnosis and at time of diagnosis of BP. We evaluate the presence of splicing factor mutations at BP. A total of 60/477 (12.5%) patients with diagnosis of BP of PV were identified, 17 of them had BM sample available during CP. Ten patients with PV CP were used as control group. We found that dyserythropoiesis during evolution were more frequent in patients who develop BP than in patients who remain in CP (13/17 vs. 3/10; P =.0402). Similarly, ring sideroblast (RS) increase during CP were more frequent in patients who develop BP (8/16 vs. 0/10. P =.0095). By ELN risk stratification for CG risk in BP all patients had adverse or intermediate risk; in AML-JAK2mut 2/11 patients (18%) had favorable as risk category. TP53 mutations were significantly more frequent in BP than in AML-JAK2mut (7/14 vs. 1/11, P =.0421). Mutation analysis for splicing factor at BP was performed on 13 patients. Only 2 patients with >15% RS had SRSF2 (2 patients) and SF3B1 (1 patient) mutations. The other patients were wild type. Dyserythropoiesis and the acquisition of RS precede other markers of disease progression to BP. CK and TP53 mutation are more frequent in BP than in AML-JAK2mut. SF3B1 mutations are rare in BP.