Risk factors for leukemic transformation include most aggressive MPN subtype, as MF; other well known risk factors are blast counts above 3–5%, age, anemia, thrombocytopenia, leukocytosis, increasing bone marrow fibrosis, type 1 CALR-unmutated status, triple negative status; adverse cytogenetics, and acquisition of ≥2 high-molecular risk mutations (ASXL1, EZH2, IDH1/2, SRSF2, and U2AF1Q157) [114]. Here, CALR is linked to anemia (phenotype).