SRSF2 and essential thrombocythemia: However, in MF and in ET, CALR-mutated MPN were under-represented among SRSF2-mutated patients (3.5 and 5.9% respectively, Table S1; versus 33% and 23% expected for CALR-mutated MF and ET) and only one of 17 SRSF2-mutated patients had a triple-negative ET (15% expected).