The New WHO classification for Essential Thrombocythemia calls for revision of available evidences


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In the 2016 revised classification of myeloproliferative neoplasms pre-fibrotic primary myelofibrosis (pre-PMF) was recognized as a separate entity, distinct from essential thrombocythemia (ET).  Owing that the majority of cases falling in the pre-PMF category were previously diagnosed as ET, one may question about the need to re-evaluate the results of epidemiologic, clinical, and molecular studies, and the results of clinical trials in the two entities.  Based on a critical review of recently published studies, pre-PMF usually presents with a distinct clinical and hematological presentation and higher frequency of constitutional symptoms.  JAK2V617F and CALR mutations in pre-PMF patients are superimposable to ET, whereas non-driver high-risk mutations are enriched in pre-PMF compared with ET.

Thrombosis is not significantly different, whereas bleeding is more frequent in pre-PMF.  Median survival is significantly shorter in pre-PMF and 10-year cumulative rates progression to overt myelofibrosis is 0–1% vs. 10–12%, and leukemic transformation is 1–2% vs. 2–6%, in ET and pre-fibrotic-PMF, respectively.  Most patients fall in the lower prognostic IPSS group in which observation alone can be recommended.  Patients at intermediate risk may require a symptom-driven treatment for anemia, splenomegaly or constitutional symptoms while cytoreductive drugs are indicated in the high-risk category.

The new WHO classification for essential thrombocythemia calls for revision of available evidences

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