MPL and myeloproliferative disorder: However, in approximately 15% of essential thrombocytosis (ET) and less than 10% of primary myelofibrosis (PMF), driver mutations are still unknown and these patients are defined as triple‐negative MPN (TN‐MPNs).11 Next‐Generation Sequencing (NGS) has identified more than 30 noncanonical MPL mutants in TN‐MPNs which are constitutional or acquired somatically.