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Myeloproliferative Neoplasms

Morbi myeloproliferativi

For medical students2 min readUpdated 2026-10-10

Myeloproliferative neoplasms are a group of disorders arising from the malignant transformation of a multipotent hematopoietic stem cell. The hallmark of these processes is that the altered cells retain the ability to undergo full differentiation while actively proliferating.

Pathogenesis basisStem cell transformation
DifferentiationCells retain maturity
Blood changesLeukocytosis and thrombocytosis
Bone marrowMegakaryocytosis and fibrosis

General Characteristics and Pathogenesis

The development of this group of disorders is based on involvement of the multipotent hematopoietic stem cell, leading to clonal proliferation of one or more myelopoietic lineages. The critical difference between these conditions and acute leukemias is that clonal cells retain the ability to differentiate into mature forms.

Clinical and morphological manifestations involve the blood system and internal organs:

Classification of Main Nosologies

The pathology includes several distinct nosological entities that differ in clinical and genetic features:

  1. Chronic myeloid leukemia (CML), Ph+ — a form associated with the Philadelphia chromosome marker.
  2. Chronic neutrophilic leukemia.
  3. Chronic eosinophilic leukemia, also known as hypereosinophilic syndrome.
  4. Primary myelofibrosis (chronic idiopathic myelofibrosis).
  5. Polycythemia vera (Vaquez disease).

Focus on Chronic Myeloid Leukemia

Among all nosologies, CML with the Philadelphia chromosome deserves special attention. This genetic alteration represents a specific chromosomal rearrangement.

This genetic marker serves as a key diagnostic criterion for verifying this form among other myeloproliferative disorders.

Mnemonic

"Myelo-PRO-proliferation — cells PRO-ceed to differentiate" (the main distinction from acute leukemias).

Frequently asked questions

What bone marrow changes are characteristic of myeloproliferative neoplasms?

Myeloproliferative neoplasms are characterized by bone marrow changes associated with the clonal proliferation of one or more myelopoietic lineages while preserving the cells' capacity for differentiation.

Bone marrow findings may include:

  • Increased number of megakaryocytes.
  • Development of fibrosis.
  • In polycythemia vera — panmyelosis, meaning hypercellularity of the erythroid, granulocytic, and megakaryocytic lineages.
What peripheral blood changes are typical for myeloproliferative neoplasms?

Typical peripheral blood changes in myeloproliferative neoplasms include an elevation in one or more types of formed blood elements.

Key manifestations include:

  • Leukocytosis.
  • Thrombocytosis.
  • Elevated counts of one or more blood cell lineages.
  • Chronic myeloid leukemia is characterized by eosinophil-basophil association — a simultaneous increase in the number of eosinophils and basophils.
What stages are distinguished in the clinical course of chronic myeloid leukemia?

The clinical course of chronic myeloid leukemia comprises three sequential phases.

  • Chronic phase — a monoclonal phase lasting 3 to 5 years, with a blast percentage of 1–3%.
  • Accelerated phase — an intermediate stage of progression.
  • Blast crisis (blast transformation) — the terminal stage characterized by decreased cellular differentiation, polyclonal proliferation, and high treatment resistance.
What macroscopic and microscopic changes occur in the spleen in chronic myeloid leukemia?

Chronic myeloid leukemia features splenomegaly associated with extramedullary hematopoiesis and leukemic infiltration.

  • Macroscopic changes: spleen weight can exceed 3 kg, consistency is firm, and the cut surface has a mottled appearance. Infarct areas may occur due to vascular occlusion by clusters of tumor cells (leukemic thrombi).
  • Microscopic changes: the red pulp is engorged with leukemic cells, and lymphoid follicles are replaced by massive overgrowths of leukemic cells. Leukemic infiltrates may be located along the interstitium, around vessels, and within their walls; infiltration is often diffuse.
Which genetic mutation is a specific marker for polycythemia vera?

A specific genetic marker for polycythemia vera is a mutation in the JAK2 gene. According to WHO diagnostic criteria, confirmation of diagnosis requires detecting the JAK2 V617F mutation (also denoted as V617ZF) or a mutation in exon 12 of the JAK2 gene as a major criterion.

What are the main complications and causes of death in polycythemia vera?

The main causes of death in polycythemia vera are complications related to hypertension and thrombosis. Characteristic complications include:

  • Thrombotic events — myocardial infarction, ischemic stroke, pulmonary infarction, and digital gangrene.
  • Tumor progression — transformation of the disease into myelofibrosis or acute myeloid leukemia.
What is the main mechanism of development of myeloproliferative neoplasms?

It is based on the malignant transformation of a multipotent hematopoietic stem cell, leading to clonal proliferation of one or more myelopoietic lineages.

What key feature distinguishes these diseases from other leukemias?

The key feature is that the clonal cells fully retain their ability to differentiate.

What causes hepatosplenomegaly in these pathologies?

The enlargement of the liver and spleen is driven by the development of foci of extramedullary hematopoiesis.

What genetic feature is characteristic of chronic myeloid leukemia?

It is characterized by the presence of the Philadelphia chromosome, resulting from the t(9;22)(q34;q11) translocation with the formation of the bcr/abl chimeric gene.

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