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

Table 6 The 2000 European Clinical and Pathological criteria for the diagnosis of polycythemia vera defined by Michiels[73] in 1997[9,74], and in 2000[93]

Clinical ECP criteria of PV	Pathological ECP criteria of PV
A1 Increased erythrocytes > 6 × 1012/L. Raised RCM: RCM (optional) male > 36 mL/kg, female > 3.2 mL/kg or increased red cell counts above 6 × 1012/L	B1 Thrombocytheia: platelet count > 400 × 109/L
A2 Absence of any cause of primary or secondary erythrocytosis by clinical and laboratory investigations	B2 Granulocytes > 10 × 109/L and raised LAP score in the absence of fever or infection
A3 Histopathology of bone marrow biopsy	B3 Splenomgaly on palpation or on echogram > 11 cm
(1) Increase and clusters of pleomorph large megakaryocytes with hyperploid nucei	B4 Spontaneous erythroid colony formation in the absence of EPO and low plasma or serum EPO level
(2) Increased cellulartity due to increased erythropoiesis or erythropoiesis and granulopoiesis (panmyelosis)	Staging of MF related to reticulin fibrosis
(3) No or slight increase of reticulin fibers	MF 0 No reticulin fibrosis RF 0/1
	MF 1 Slight reticulin fibrosis RF 2
	MF 2 Marked increase RF grade 3 and slight to moderate collagen fibrosis
	MF 3 Advanced collagen fibrosis-osteosclerosis

Diagnosis of idiopathic erythrocythemia (IE), early prodromal polycythemia vera (PV), classical PV or latent primary myeloproliferative disease (subclinical PV) are acceptable when[73,74,93]: A1 + A2 + A3 and none of B (except B4) is consistent with early erythrocythemic PV, labelled as idiopathic erythrocythemia: IE; A3 + B1 + B4 is consistent with prodromal PV with PV features in the bone marrow; A1 + A2 + A3 + plus one of B1 to 3 is consistent with classical PV; B4 confirms all variants of IE, prodromal PV and classical PV; A3 + B3 and none of the others is consistent with latent subclinical primary myeloproliferative diease (PMD) usually preceding masked cases of PV or MF during long term follow-up. ECP: European Clinical and Pathological; MF: Myelofibrosis; RF: Reticulin fibrosis; EPO: Erythropoetin; RCM: Red cell mass; LAP: Leukocyte alkaline phosphatase.