CALR mutations, together with JAK-2 and MPL ones, are recognized as “driver” mutations in Philadelphia-negative chronic myeloproliferative neoplasms (MPNs). Most frequent Type-1 deletions (45-55% of cases) type-2 insertion (32-42% cases). These usually associated younger age, higher platelet counts, lower leukocyte hemoglobin levels a incidence transformation from ET to MF. Recognizing describi...