The identification of somatic mutations of CALR in MF came in the form of two primary studies, one of which was published in 2013 by Klampfl and authors, who observed that an estimated 30–45% of patients with either primary myelofibrosis (PMF) or essential thrombocythemia (ET) had no previously known identifiable clonal mutations, including JAK2 and MPL mutations [29]. This evidence concerns the gene CALR and primary myelofibrosis.