The relation of SF3B1 mutation and intracellular iron in myelodysplastic syndrome with less than 5% bone marrow blasts.

According to 2008 WHO classification RARS is regarded as less than 5% blasts and more than 15% ring sideroblasts in the bone marrow. In 2016 WHO classification MDS-RS is revised as more than 15% ring sideroblasts or more than 5% ring sideroblasts in the presence of the SF3B1 mutation. In our study, we classified intracellular iron in bone marrow into four types according to the size and quantity of iron granules. We found that there was a significant difference between SF3B1-mutant and SF3B1-wild-type MDS patients in intracellular iron III, intracellular iron IV and ring sideroblasts. We defined intracellular iron (III + IV + RS)%×100 as 'Iron score'. We suggest that the patients carrying SF3B1 mutation with Iron score ≥10 will extend the subtype of MDS-RS, in addition to the current WHO classification criteria. This study gives us a new insight into the relation of SF3B1 mutation and intracellular iron in lower-risk MDS.