Table 5.

2016 World Health Organization (WHO) criteria for the diagnosis of pre-fibrotic primary myelofibrosis²

Major criteria

1. Megakaryocytic proliferation and atypia, without reticulin fibrosis >grade 1, accompanied by increased age-adjusted BM cellularity, granulocytic proliferation and often, decreased erythropoiesis

2. Not meeting WHO criteria for CML, PV, ET, MDS, or other myeloid neoplasms

3. Presence of JAK2, CALR, or MPL mutation or, in the absence of these mutations, presence of another clonal marker, e.g., mutations in ASXL1, EZH2, TET2, IDH1, IDH2, SRSF2, SF3B1, or absence of minor reactive bone marrow reticulin fibrosis

Minor criteria

1. Anemia not attributed to a comorbid condition

2. Leukocytosis ≥11 × 109/L

3. Palpable splenomegaly

4. LDH above institutional upper limit of normal

Diagnosis requires meeting all three major criteria and at least one minor criterion. CML, chronic myeloid leukemia; PV, polycythemia vera; ET, essential thrombocythemia; MDS, myelodysplastic syndromes.