Diagnostic Criteria
(Barosi et al, Br J Haematol 1999)

Necessary criteria
A. Diffuse bone marrow fibrosis
B. Absence of Philadelphia chromosome or BCR-ABL rearrangement
in peripheral blood cells

Optional criteria
1. Splenomegaly of any grade
2. Anisopoikilocytosis with tear-drop erythrocytes
3. Presence of circulating immature myeloid cells
4. Presence of circulating erythroblasts
5. Presence of cluster of megakaryoblasts and anomalous megakaryocytes
in bone marrow sections
6. Myeloid metaplasia
Diagnosis of MMM is acceptable if the following combinations are present: the two necessary criteria plus any other two optional criteria when splenomegaly is present; the two necessary criteria plus any other four optional criteria when splenomegaly is absent.