MF: all 3 major criteria and at least 1 minor criterion confirmed in 2 consecutive determinations

MAJOR
Proliferation and atypia of megakaryocytes plsu reticulin and/or collagen fibrosis grades 2-3 on a scale of 0-3
Not meeting WHO criteria for ET, PV, BCR-ABL1+ CML, myelodysplastic syndromes, or other myeloid neoplasm
Presence of JAK2, CALR or MPL mutation or presence of another clonal markera or absence of reactive myelofibrosis

MINOR
Anemia not attributed to a comorbid condition
Leukocytosis ≥11 x 109/L
Palpable splenomegaly
LDH increased 
Leukoerythroblastosis


PV: Diagnosis requires meeting either all 3 major criteria or the first 2 major criteria and the minor criterionc

MAJOR

Hb >16.5 g/dL in men, >16.0 g/dL in women, or Hct >49% in men, >48% in women, or increased red cell mass >25% above mean normal predicted value
Bone marrow biopsy showing hypercellularity for age with trilineage growth (panmyelosis), including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature megakaryocytes (differences in size)
Presence of JAK2 V617F or JAK2 exon 12 mutation

MINOR
Subnormal serum erythropoietin level

c
Major criterion number 2 (BM biopsy) may not be required in cases with sustained absolute erythrocytosis: Hb levels >18.5 g/dL in men (hematocrit 55.5 %) or >16.5 g/dL in women(hematocrit 49.5%) if mutation criterion 3 and the minor criterion are
present. However, initial MF (present in up to 20% of patients) can only be detected by performing a BM biopsy; hypercellularity may predict a more rapid progression to overt MF (post-PV MF).

ET: Diagnosis requires meeting all 4 major criteria or the first 3 major criteria and the minor criterion

MAJOR
TR ≥450 x 109 /L
Bone marrow biopsy: proliferation mainly of the megakaryocyte lineage with increased numbers of enlarged, mature megakaryocytes with hyperlobulated nuclei; no significant increase or left-shift in neutrophil granulopoiesis or erythropoiesis and very rarely minor (grade 1) increase in reticulin fibers.
Not meeting WHO criteria for BCR-ABL1+ CML, PV, PMF, myelodysplastic syndromes, or other myeloid neoplasms
Presence of JAK2, CALR, or MPL mutation.

MINOR:
Presence of a clonal marker or absence of evidence for reactive thrombocytosis