European vs 2015-World Health Organization clinical molecular and pathological classification of myeloproliferative neoplasms

Table 7 2015 World Health Organization Clinical Molecular and Pathological criteria for the diagnosis of prodromal, masked and classical JAK2 mutated polycythemia vera vs primary or secondary erythrocytoses[77,78]

CM criteria	Bone marrow pathology (P) criteria (WHO)
Major criteria for PV	P1 Bone marrow pathology: increased cellularity (60%-100%) due to trilinear increase of erythropoiesis, megakaryopoiesis and granulopoiesis and clustering of small to giant (pleomorph) megakaryocytes with hyperlobulated nuclei
A1 Hematocrit > 0.51/> 0.48 in male/female Erythrocytes > 5.8 × 1012/L males > 5.6 × 1012/L females	Absence of stainable iron. No pronounced inflammatory reaction
A2 Presence of heterozygous and/or homozygous JAK2V617F or JAK2 exon 12 mutation	P2 Erythrocytosis. Normal erythropoiesis, normal granulopoiesis and megakaryocytes of normal size, morphology and no clustering
A3 Low serum Epo level	Grading of RF and MF
Minor	Prefibrotic: RF-0/1 = MF-0
B1 Persistent increase of platelet count × 109/L:	Early fibrotic: RF-2 = MF-1
grade 1: 400-1500, grade 2: > 1500	Fibrotic: RCF 3 = MF-2
B2 Granulocytes > 10 × 109/L or Leukocytes > 12 × 109/L and raised	Post-PV MF: RF 4 = MF-3
LAP-score or increased CD11b expression in the absence of fever or infection
B3 Splenomegaly on ultrasound echogram (> 12 cm length in diameter) or on palpation
B4 Spontaneous EEC formation (optional)

2015 WHO-CMP criteria for staging of prodromal, erythrocythemic, and advanced polycythemia vera (PV). A2 + B1 + P1 establish early PV (mimicking ET) prodromal PV CMP stage 0; A1 + A2 + A3 + P1 and none of B establish idiopathic erythrocythemia (IE) or stage 1 PV; A1 + A2 + A3 + P1 and one or more of B establish classic stages of PV stage 2 and 3; A2 + B3 + P1 detect masked cases of PV with splenomegaly and hypersplenism to be labelled as inapparent PV (IPV) frequently seen Budd-Chiari syndrome or splanchnic vein thrombosis. CM: Clinical and molecular; RF: Reticulin fibrosis; MF: Myelofibrosis; ET: Essential thrombocythemia; WHO-CMP: World Health Organization clinical molecular and pathological; EEC: Endogenous erythroid colony.