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Chronic Myeloid Neoplasms

Myeloproliferative neoplasms (MPN) - general

Reviewer: Nikhil Sangle, M.D., University of Utah & ARUP Laboratories (see Reviewers page)
Revised: 8 August 2011, last major update August 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Clinical features

● First described by William Dameshek in 1951 (Blood 1951;6:372)
● WHO 2001: termed chronic myeloproliferative diseases
● WHO 2008: termed myeloproliferative neoplasms, to emphasize the clonal evolution of these entities
● All have effective clonal myeloproliferation with no dyserythropoiesis, no granulocyte dysplasia and no monocytosis; their phenotypic diversity is due to different mutations affecting tyrosine kinases or related molecules, causing different patterns of abnormal signal transduction
● Initially hypercellular marrow with increased hematopoiesis, increased peripheral blood counts (often marked increase in all cell lines but with normal morphology) and extramedullary hematopoiesis in spleen with splenomegaly / other organomegaly; then spent phase with marrow fibrosis and cytopenia
● CML frequently progresses to acute myelogenous leukemia (AML), but other myeloproliferative neoplasms only rarely progress to AML
● There is considerable morphologic overlap among subtypes and with benign hyperplastic marrow conditions, requiring a multimodal diagnostic approach combining cytomorphology, cytogenetics and molecular methods for BCR/ABL-negative cases (Ann Hematol 2008;87:1)
● 4 color flow cytometry is helpful in diagnosis (Arch Pathol Lab Med 2003;127:1140)
● Extramedullary hematopoiesis appears to be a clonal process (Hum Pathol 2007;38:1760) with JAK2 V617F mutation frequently present in splenic EMH cells (Mod Pathol 2007;20:929)
● Occasionally has coexisting monoclonal B cell infiltrate in bone marrow detectable by IgH PCR, but not by morphology (Mod Pathol 2004;17:1521)
● May have nodal or extranodal tumor-forming accumulations of plasmacytoid monocytes / interferon-producing cells, which are clonal, and related to underlying myeloid tumor (Am J Surg Pathol 2004;28:585)
● Associated with chronic thromboembolic pulmonary hypertension and pulmonary arterial hypertension (Respiration 2008;76:295)
● Usually prolonged survival

Micro description

● May have emperipolesis (ingestion of blood cells by megakaryocytes or other cells)
● Rarely monocytic nodules similar to plasmacytoid monocyte nodules (Am J Clin Pathol 2003;120:874)

Molecular description

● JAK2 V617F mutation (Janus kinase 2 gene) present in most non-CML chronic myeloproliferative diseases (>85% of polycythemia vera, 65% of essential thrombocythemia, 65% of chronic idiopathic myelofibrosis, Am J Surg Pathol 2007;31:233), causes constitutive tyrosine kinase activity
● c-MPL mutation (thrombopoietin receptor) occurs in essential thrombocythemia and idiopathic myelofibrosis (J Transl Med 2006;4:41)
● FLT3 mutations are occasionally seen (Am J Clin Pathol 2006;126:530)

Molecular images

Drawing of JAK2 mutation

Drawing of c-Mpl mutation

End of Chronic Myeloid Neoplasms > Myeloproliferative neoplasms (MPN) - general

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