Proposed revised WHO criteria for essential thrombocythemia (ET)
| Proposed criteria for ET . |
|---|
| 1. Sustained platelet count ≥ 450 × 109/L* |
| 2. Bone marrow biopsy specimen showing proliferation mainly of the megakaryocytic lineage with increased numbers of enlarged, mature megakaryocytes; no significant increase or left-shift of neutrophil granulopoiesis or erythropoiesis |
| 3. Not meeting WHO criteria for PV,† PMF,‡ CML,§ MDS,¶ or other myeloid neoplasm |
| 4. Demonstration of JAK2617V>F or other clonal marker, or in the absence of a clonal marker, no evidence for reactive thrombocytosis∥ |
| Proposed criteria for ET . |
|---|
| 1. Sustained platelet count ≥ 450 × 109/L* |
| 2. Bone marrow biopsy specimen showing proliferation mainly of the megakaryocytic lineage with increased numbers of enlarged, mature megakaryocytes; no significant increase or left-shift of neutrophil granulopoiesis or erythropoiesis |
| 3. Not meeting WHO criteria for PV,† PMF,‡ CML,§ MDS,¶ or other myeloid neoplasm |
| 4. Demonstration of JAK2617V>F or other clonal marker, or in the absence of a clonal marker, no evidence for reactive thrombocytosis∥ |
Diagnosis requires meeting all 4 criteria.
During the work-up period.
Requires the failure of iron replacement therapy to increase hemoglobin level to the PV range in the presence of decreased serum ferritin. Exclusion of PV is based on hemoglobin and hematocrit levels, and red cell mass measurement is not required.
Requires the absence of relevant reticulin fibrosis, collagen fibrosis, peripheral blood leukoerythroblastosis, or markedly hypercellular marrow for age accompanied by megakaryocyte morphology that is typical for PMF− small to large with an aberrant nuclear/cytoplasmic ratio and hyperchromatic, bulbous or irregularly folded nuclei and dense clustering.
Requires the absence of BCR-ABL.
Requires absence of dyserythropoiesis and dysgranulopoiesis.
Causes of reactive thrombocytosis include iron deficiency, splenectomy, surgery, infection, inflammation, connective tissue disease, metastatic cancer, and lymphoproliferative disorders. However, the presence of a condition associated with reactive thrombocytosis does not exclude the possibility of ET if the first three criteria are met.