In the group of Ph-negative MPN preceding CML (9/24 cases), CALR was evaluated and found positive at initial Ph-negative MPN diagnosis only in 2/9 cases (Bonzheim et al., 2015), whereas in 7/9 cases, the CALR test was not performed at initial diagnosis because the test was not available. Here, CALR is linked to myeloproliferative neoplasm.