Furthermore, the earliest stage in this biological continuum–genuine ET—also includes “triple-negative” ET patients with no JAK2V617F, CALR or MPL mutations and an exceedingly favourable prognosis, suggesting that these patients may have a less severe form of ET or, alternatively, that some of these “ET” patients may actually not have any overt MPN but rather thrombocytosis associated with a more benign process [68–69]. This evidence concerns the gene CALR and essential thrombocythemia.