Megakaryocytes abnormalities and where there are seen
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megakaryocyte dysplasia
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megakaryocyte morphology abnormalities hypolobated micromegakaryocytes diseases hematopathology
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https://www.pathologyoutlines.com/topic/myeloproliferativemy…
Megakaryocytic abnormalities are assessed mainly in bone marrow aspirate/biopsy.
| Abnormality | Typical appearance | Seen in |
|---|---|---|
| Micromegakaryocytes | Very small megakaryocytes, sometimes lymphocyte-sized | Myelodysplastic syndrome (MDS), especially MDS with isolated del(5q); also myeloproliferative neoplasms (MPN) and primary myelofibrosis |
| Hypolobated or non-lobated nuclei | Single, bilobed, or poorly segmented nucleus | MDS, particularly del(5q) MDS |
| Multiple separate nuclei / “pawn-ball” nuclei | Several round nuclei rather than one multilobated nucleus | MDS and other dysmegakaryopoietic states |
| Large megakaryocytes with hyperlobated nuclei | Excessively large cells with deeply lobulated “staghorn” nuclei | Essential thrombocythemia (ET), also polycythemia vera |
| Bulbous, cloud-like, bizarre hypolobated nuclei | Markedly atypical forms, variable cell size, often in clusters | Primary myelofibrosis (PMF), including prefibrotic PMF |
| Megakaryocyte clustering | Dense or loose groups in marrow biopsy | MPN, most characteristically ET and PMF |
| Increased megakaryocytes | Megakaryocytic hyperplasia | Reactive thrombocytosis, immune thrombocytopenia (often increased young forms), ET, PV, CML, PMF |
| Decreased or absent megakaryocytes | Reduced platelet precursor cells | Aplastic anemia, marrow failure, some congenital amegakaryocytic thrombocytopenias |
| Dysplastic cytoplasm | Hypogranular or agranular cytoplasm, pseudopods | MDS and MPN/MDS overlap disorders |
High-yield associations
- MDS: micromegakaryocytes, hypolobated/non-lobated nuclei, multinucleated forms. Micromegakaryocytes are considered the most specific morphologic marker of megakaryocytic dysplasia.
- MDS with isolated del(5q): classic small hypolobated micromegakaryocytes. The NIH description of del(5q) MDS specifically notes hypolobated micromegakaryocytes.
- Essential thrombocythemia: many large, mature, hyperlobulated megakaryocytes, often in clusters.
- Primary myelofibrosis: atypical megakaryocytes with marked variation in size and bulbous hypolobated nuclei, often forming clusters, with reticulin/collagen fibrosis. Pathology Outlines summarizes these marrow features.
- Peripheral blood micromegakaryocytes: may occur in advanced primary myelofibrosis and reflect severe marrow disruption/extramedullary hematopoiesis.
A quick memory aid: MDS = small and hypolobated; ET = large and hyperlobated; PMF = bizarre, bulbous, clustered.
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