SF3B1 and myelodysplastic syndrome: Comparison of the 158 patients with MDS/MPN-RS-T and the 25 patients with MDS/MPN-U-RS revealed a higher frequency of SF3B1 mutations (92% versus 40%, P = 0.003, Fig. 3A) and AML transformation rate (4% versus 0%, P = 0.0003) in MDS/MPN-RS-T (Table 1).