Bone marrow histopathology in Ph - CMPDs - the new WHO classification - Juergen Thiele Cologne, Germany
Current issues in MPNs concerning morphology 1.Prodromal stages of disease 2.Impact of histopathology for diagnosis 3. Clinical-histopathological correlations 4. Discrimination between subtypes 5. Reproducibility of histological features
Proposed modified WHO histological criteria -PV- Minor criteria 1.Bone marrow biopsy showing panmyelosis with prominent erythroid, granulocytic, and pleomorphous megakaryocytic proliferation 2. Low serum erythropoietin level 3. Endogenous erythroid colony formation in vitro
PV SP
PV SP
SP
Discrimination between PV and SP Incidence of BM features (%) Megakaryocytes pleomorphous aspect (differences in size) PV 97 0 SP SP increased nuclear lobulation 87 11 loose clusters 63 2 naked nuclei 15 0 Stroma perivascular plasmocytosis 4 91 iron-laden macrophages 12 87 cellular debris 0 94
Overlapping between initial PV and ET 48 patients with initial-early PV Thrombocytes x10 9 /l >500 28 patients (59%) >600 24 patients (52%) >1000 6 patients ( 11%)
PV ET
PV ET
Discrimination between initial PV and ET Incidence of BM features (%) PV ET Increase in cellularity 100 0 erythropoiesis 89 9 granulopoiesis 78 21 PV Megakaryocytes giant forms 25 98 pleomorphous aspect 97 5 (differences in size)
Dynamics of the disease process in PV Evolution ~10%-15% mimicking ET JAK2 +/- JAK2 +/+ EPO Manifestation Fibrosis Splenomegaly definite increase in red cell mass 10-15 yrs. (t) Transformation Post-polycythemic myeloid metaplasia (spent phase) ~ 30 % ~ 10-15 % Blastic crisis Initial stage Polycythemic stage Terminal stage
Proposed modified WHO histological criteria -ET- 1. Sustained platelet count > 450 x 10 9 /L 2.Bone marrow biopsy specimen showing proliferation mainly of the megakaryocytic lineage with increased numbers of enlarged, mature megakaryocytes. No significant increase, left-shift of neutrophil granulopoiesis or erythropoiesis
ET PMF-0
Morphological features of distinctive impact in PMF-0/1 versus ET cellularity granulopoiesis erythropoiesis fibers (reticulin) PMF-0/1 increased increased reduced no or slight increase ET normal normal normal no increase
ET PMF-0
Megakaryocyte features of PMF-0/1 versus ET frequency histotopography size nuclear features aberrant nuclear/cytoplasmic ratio PMF-0/1 increased loose to dense clusters median to giant irregular foldings, bulbous lobulation, cloud-like features +++ ET markedly increased loose clusters or randomly distributed large to giant staghorn-like, deep lobulation no
ET PMF-0 ET
Survival in early MPNs with thrombocythemia 100 % Survival 80 60 40 20 0 Relative survival according to WHO (%) 5 yrs. 10 yrs. 15 yrs. ET 100.0 ± 4.4 99.1 ± 7.8 83.9 ± 17.6 PMF-0 92.1 ± 7.1 80.8 ± 11.7 PMF-1 83.0 ± 9.5 67.3 ± 17.8 67.9 ± 23.7 55.4 ± 29.8 n=476 0 2 4 6 8 10 12 14 Years after diagnosis ET PMF-0 PMF-1
Proposed modified WHO histological criteria -PMF- Major criteria 1. Presence of megakaryocyte proliferation and atypia, usually accompanied by either reticulin and/or collagen fibrosis, or, in the absence of remarkable reticulin fibrosis, the megakaryocyte changes must be accompanied by marked bone marrow cellularity including granulocytic proliferation and decreased erythroid precursors (i.e. pre-fibrotic cellular-phase disease).
Proposed modified WHO histological criteria -PMF- Histopathology of megakaryopoiesis Small to large megakaryocytes with an aberrant nuclear/cytoplasmic ratio and hyperchromatic, bulbous, or irregularly folded nuclei and dense clustering
PMF-0
PMF-0
PMF-0
PMF-0
PMF-0 PMF-1
PMF-2 PMF-3
PMF-3
Dynamics of PMF in 865 patients Evolution Manifestation Transformation initial stage reticulin collagen fibrosis osteosclerosis (t) PMF blast phase BM -insufficiency 13.9 854 5.0 2.9 10.9 spleen size (cm) erythro-/myeloblasts (%) hemoglobin (g/dl) 629 LDH (U/l) 1.0 284 0 276 thrombocytes (x 10 9 /l) Prefibrotic-early PMF Advanced PMF (MMM)
Dynamics of myelofibrosis in prodromal PMF* (bone marrow histology) Initial stage MF-0 MF-1 MF-2 MF-3 Prefibrotic (MF-0) 10% (stable) 42% (progression) 20% (progression) 28% (progression) Early fibrotic (MF-1) 5% (regression) 31% (stable) 32% (progression) 32% (progression) * 300 patients (intervals ranging between 3 to 5 years)
Risk of myelofibrosis in 180 patients with early PMF 1.0 Bone marrow fibrosis 0.8 Probability (%) 0.6 0.4 MMM (AMM) 0.2 median [95% CI] MMM (AMM) 108 [79-137] BM fibrosis 44 [29-59] 0 0 20 40 60 80 100 120 Months after diagnosis 140 160
UK-PT1 - Study 809 patients with high risk ET (PVSG criteria) After 39 months 21 patients (2.6%) showed overt myelofibrosis with myeloid metaplasia (Harrison et al N. Engl. J. Med. 2005; 353: 33-45)
Risk of myelofibrotic transformation within 36 months in 539 high-risk ET patients Incidence of myelofibrosis (%) PVSG ET ET WHO classification Prefibrotic/ early PMF according to clinical definition 2.2 0 2.8 according to increase in BM fibers 10.8 0 13.6 overall incidence 2.8 0 3.5* * p=0.002 (two-sided exact significance) for ET versus prefibrotic/early stages of PMF
Survival rates in PMF according to stage 100 80 prodromal PMF %Survival 60 40 manifest PMF (MMM/AMM) 20 Stage n prodromal 565 overt 300 Relative survival rates (%) 5 yrs. 10 yrs. 15 yrs. 87 72 59 70 49 32 0 0 2 4 6 8 10 12 14 Years after diagnosis
Prognostic features in early as well as overt PMF (multivariate risk classification) Age; Hemoglobin; Leukocytes; Platelets; Peripheral blood precursors; Cytogenetic abnormalities; extramedullary hematopoiesis
Loss of life expectancy in Ph - MPNs with thrombocythemia 16.5% PVSG criteria ET Histopathology (WHO criteria) ET 8.9% PMF-0 21.6% 32.3% PMF-1!! 37.5% PMF classical PMF-2 & PMF-3 37.5% 20.3% PV PV 20.3% 40 30 20 10 Loss of life expectancy 0 0 10 20 30 40 Loss of life expectancy
Bone marrow in early stage MPDs PV ET Marked variation of megakaryocyte sizes (pleomorphic aspect), dispersed or loosely clustered. Prominent proliferation of granulopoiesis and erythroid precursors Prominent large to giant megakaryocytes with deeply folded nuclei, dispersed or loosely clustered. No significant increase in granulo- and erythropoiesis PMF (initialearly stage) Dense clustering of medium sized to giant megakaryocytes showing bulbous nuclei (maturation defects). Pronounced proliferation of granulopoiesis and reduction of erythroid precursors Megakaryopoiesis Granulopoiesis Erythropoiesis
Reproducibility of histological features (WHO classification) Yes Florena, AM et al. Haematologica, 2004, 89:911-919 Tripodo, C et al. Histol. Histopathol, 2006, 21:813-821 Gianelli, U et al. Leuk. Lymphoma. 2006, 47:1774-1781 No Wilkens, BS et al. Blood, 2007 online
Design of the study by Wilkens et al. (370 patients) 1.No training set for standardization 2.No clear definition of parameters (cloud-like, hyperlobulated, pyknotic, dysplastic megakaryocytes) 3.Small size of biopsies (> 0.5 cm) 4.No self-assessment (intra-observer evaluation)
Inter-observer reliability Yes Overall cellularity Reticulin fiber grade New bone formation Megakaryocytic and granulocytic cellularity No WHO classification Erythroid cellularity Megakaryocyte features (except bare nuclei, number and size of clusters)
Association of parameters Overall cellularity with granulocyte and megakaryocyte cellularity (hypercellular stages of PMF?) Reticulin fiber grade with WHO diagnosis (?) No relationship between new bone formation and fibers or cellularity
Non-characteristic features of ET at onset 1. New bone formation (osteosclerosis) 2. Increase in fibers ( 2 according to grading)
Progression to myelofibrosis 143/370 cases (31,101,39) identified as prefibrotic myelofibrosis No definition of myelofibrosis Median follow-up 68 months No transformation
Conclusion I Differential diagnosis of early MPDs is based on the recognition of histological patterns and standardized features By regarding these features early stages of PMF are clearly separated from true ET In initial/early PV, which may present with an excess of platelets that mimics ET or a transitional ET/PV disorder, bone marrow histopathology is of value
Conclusion II The WHO classification is not aimed to capture all biological true cases of disease or guarantee 100% diagnostic specifity. However, it tries to combine clinical with morphological findings and incorporates the acquired JAK2V617F mutation.