CALR and myeloproliferative neoplasm: For example, in a study evaluating the prevalence of MPN driver mutations in 928 Chinese patients, the JAK2 V617F and CALR exon 9 dual mutation was identified in six (0.6%) patients, and the coexistence of JAK2 V617F and MPL exon 10 was even more uncommon, occurring in two (0.2%) patients [9].