[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [White cells, lymph nodes, spleen and thymus](https://durgical.com/en/general-pathology/areas/hematolymphoid/) › Myelodysplastic neoplasms

# Myelodysplastic neoplasms

- Lesion

A marrow full of faulty cells that die before leaving: the blood is low, the marrow is busy, and leukaemia may follow.

Updated Nov 12, 2026

## Key points

- Hypercellular marrow with peripheral cytopenias: the signature of ineffective haematopoiesis.
- Dysplasia: ring sideroblasts and megaloblastoid erythroid cells; pseudo-Pelger–Huët (bilobed) and hypogranular neutrophils; small mononuclear megakaryocytes.
- Blasts under 20%; monosomy 5 or 7, del(5q), del(20q) and trisomy 8 are common; SF3B1 mutations go with ring sideroblasts.
- Therapy-related MDS follows alkylating agents or radiation, often with chromosome 5 or 7 loss and TP53 mutations.
- CHIP: DNMT3A, TET2 and ASXL1 mutations in normal-looking blood; linked to atherosclerosis through inflammatory macrophages.

On this page

- The basics Key points
- What it is
- Structure
- Step by step
- MDS and its look-alikes
- Markers
- Memory aid
- Elsewhere in DurgiPedia

- Clinical Clinical notes

- Study Test yourself

- Connections Connections

## What it is

Myelodysplastic neoplasms (MDS) are clonal stem cell disorders in which the marrow, usually hypercellular, produces cells that are dysplastic and die early (ineffective haematopoiesis), so the blood shows cytopenias. Blasts are increased but stay below the threshold of acute leukaemia, and MDS often progresses to AML. Clonal haematopoiesis of indeterminate potential (CHIP) is a common precursor in older adults: blood cells carry leukaemia-type mutations without cytopenias, with a raised risk of MDS, AML and cardiovascular disease.

## Structure

- Erythroid: nuclear budding, multinucleation, megaloblastoid change, ring sideroblasts on Prussian blue (iron-laden mitochondria around the nucleus).
- Granulocytic: hypogranular cytoplasm, pseudo-Pelger–Huët nuclei.
- Megakaryocytes: small with single or separated nuclei.
- Blood: macrocytes, giant platelets, pseudo-Pelger cells, sometimes monocytosis.

## Step by step

- Mutations in epigenetic regulators (TET2, DNMT3A) in a stem cell give it a slight growth advantage (clonal haematopoiesis).
- Mutations in RNA splicing genes (SF3B1, SRSF2, U2AF1), transcription factors (RUNX1) or TP53 follow.
- The clone still differentiates, but abnormally; most precursors die in the marrow.
- The blood becomes cytopenic despite a full marrow.
- Further lesions block differentiation: blasts rise and AML develops.

## MDS and its look-alikes

| Disorder | Marrow cellularity | Dysplasia and blasts | Key clue |
| --- | --- | --- | --- |
| Myelodysplastic neoplasm | Usually high | Multilineage dysplasia, blasts under 20% | Clonal cytogenetic or gene mutations |
| Acute myeloid leukaemia | High | Blasts 20% or more, or a defining genetic lesion | Rapid onset |
| [Aplastic anaemia](https://durgical.com/en/conditions/aplastic-anaemia/) | Very low, fat-filled | No dysplasia, no excess blasts | Often PNH clones, no splenomegaly |
| [Megaloblastic anaemia](https://durgical.com/en/conditions/megaloblastic-anaemia/) | High | Megaloblastic change in all lines, no clonal genetics | Low B12 or folate; corrects with vitamins |

## Markers

- Prussian blue for ring sideroblasts
- CD34 blast count
- Karyotype
- SF3B1, TP53 sequencing

## Clinical notes

- Older adults (mean age around seventy) with fatigue, infections and bleeding; often found on a routine count.
- Prognosis depends on blasts, depth of cytopenias and karyotype; isolated del(5q) responds to thalidomide-like drugs.
- Chronic transfusion can lead to iron overload.

## Memory aid

A busy factory with empty shelves: MDS makes plenty but ships nothing that works.

## Test yourself

Think of the answer, then tap the question to see it.

## Why are patients with MDS cytopenic when the marrow is hypercellular?

The clonal precursors differentiate abnormally and most die in the marrow (ineffective haematopoiesis).

## What is a pseudo-Pelger–Huët cell?

A neutrophil with only two nuclear lobes (or none), a dysplastic feature of MDS.

## What is clonal haematopoiesis of indeterminate potential?

Leukaemia-associated mutations (often DNMT3A or TET2) in blood cells of a person with normal counts; it raises the risk of myeloid neoplasms and cardiovascular disease.

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## Elsewhere in DurgiPedia

- [Hematopoiesis and bone marrow](https://durgical.com/en/histology/hematopoiesis-and-bone-marrow/)

## Connections

## Related 5

- [Acute myeloid leukaemia](https://durgical.com/en/general-pathology/acute-myeloid-leukaemia/)
- [White-cell neoplasms: classification](https://durgical.com/en/general-pathology/white-cell-neoplasms-classification/)
- [Megaloblastic anaemias: B12 and folate](https://durgical.com/en/general-pathology/megaloblastic-anaemias-b12-and-folate/)
- [Aplastic anaemia](https://durgical.com/en/general-pathology/aplastic-anaemia/)
- [Hemochromatosis: hepcidin, HFE and where iron settles](https://durgical.com/en/general-pathology/hemochromatosis-hepcidin-hfe-and-where-iron-settles/)

## Related conditions 4

- [Myelodysplastic syndromes](https://durgical.com/en/conditions/myelodysplastic-syndromes/)
- [Sideroblastic anaemia](https://durgical.com/en/conditions/sideroblastic-anaemia/)
- [Acute leukaemia (AML and ALL)](https://durgical.com/en/conditions/acute-leukaemia/)
- [Aplastic anaemia](https://durgical.com/en/conditions/aplastic-anaemia/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Myelodysplastic Syndromes Treatment (PDQ®)–Patient Version](https://www.cancer.gov/types/myeloproliferative/patient/myelodysplastic-treatment-pdq) (National Cancer Institute (NCI), 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/myelodysplastic-neoplasms/