Primary Myelofibrosis (PMF)
Epidemiology and Etiology:
Common sites:
Gross features:
Histologic features:
- Semiquantitative
bone marrow fibrosis grading (MF):
- MF-0
- Scattered linear reticulin
with no intersections (cross-overs)
- MF-1
- Loose network of reticulin
with many intersections, especially perivascular
- MF-2
- Diffuse and dense increase in reticulin with extensive intersections
- occasionally with focal bundles of collagen
- and/or focal osteosclerosis
- MF-3
- Diffuse and dense increase in reticulin with extensive intersections
- Coarse bundles of collagen
- Often associated with osteosclerosis
- (Fibre density should
only be assessed in haematopoietic areas)
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- Diagnostic criteria (3 major, and at least 2
minor required)
- Major criteria:
- Megakaryocyte proliferation and atypia accompanied by reticulin
and/or collagen fibrosis
- Atypia: small to large megakaryocytes with an
aberrant nuclear/cytoplasmic ratio and hyperchromatic,
bulbous, or irregularly folded nuclei and dense clustering
- In absence of significant reticulin
fibrosis, bone marrow cellularity must be significant, characterized
by granulocytic proliferation and often decreased erythropoiesis (i.e.
prefibrotic cellular-phase disease)
- Not meeting WHO criteria for PV, BCR-ABL1+
CML, MDS, or other myeloid neoplasms
- Absence of BCR-ABL1
- Requires failure of iron replacement therapy
to increase Hb level to the PV range in the
presence of decreased serum ferritin.
Exclusion of PV is based on Hb and haematocrit levels
- Absence of dyserythropoiesis
and dysgranulopoiesis
- JAK2 V617F or other clonal marker (ex. MPL
W515K/L), OR
- No evidence of a secondary cause of marrow
fibrosis or other changes:
- Infection
- Autoimmune disorder
- Chronic inflammatory condition
- hairy cell leukaemia
- other lymphoid neoplasm
- metastatic malignancy
- toxic (chronic) myelopathies
- Minor criteria:
- Leukoerythroblastosis (borderline or marked)
- Increase in serum LDH (borderline or marked)
- Anaemia (borderline or marked)
- Splenomegaly (borderline or marked)
References:
- Swerdlow
et al. WHO Classification of Tumours of Haematopoietic
and Lymphoid Tissues (2008)