Definition of a distinct MDS disease subtype characterized by somatic mutations in SF3B1. MDS patients with somatic SF3B1 mutations share a common phenotype, with favorable outcomes and a restricted spectrum of subclonal mutations, independently of their WHO 2017 category. Malcovati et al propose a new MDS subtype characterized by SF3B1 mutations, following the classification criteria depicted in the figure. Abn, abnormalities; BM, bone marrow; CK, complex karyotype (≥3 chromosomal alterations); MLD, multilineage dysplasia; MPN, myeloproliferative neoplasms; PB, peripheral blood; SLD, single-lineage dysplasia.