Circulating Blasts
September 8th, 2021
Overview
Blasts are not usually present in the peripheral blood; their presence in the circulation is highly abnormal and classically suggestive of acute leukaemia.
Blasts tend to be medium to large cells with a large nucleus that takes up most of the cell (high nuclear : cytoplasmic ratio), fine nuclear chromatin pattern, nucleoli and a grey to blue cytoplasm.
Types of Blasts
- Myeloblast - medium to large cells with high nuclear:cytoplasmic ratio, fine nuclear chromatin, prominent nucleoli, pale blue cytoplasm and intracytoplasmic vacuolesSeen in acute myeloid leukaemia
- Monoblast - large cells with low to moderate nuclear:cytoplasmic ratio, delicate lacy chromatin, large and prominent nucleoli and light grey cytoplasmSeen in acute monoblastic and myelomonoblastic leukaemia
- Lymphoblast - small to medium cells with high nuclear:cytoplasmic ratio, open nuclear chromatin, less prominent nucleoli and basophilic cytoplasm without granulesSeen in acute lymphoblastic leukaemia
- Megakaryoblast - small to medium cells with round or indented nuclei, fine reticular chromatin and basophilic cytoplasm with cytoplasmic blebbingSeen in acute megakaryocytic leukaemia and myeloid neoplasms associated with Down syndrome
Causes of Circulating Blasts
- Acute leukaemia - acute myeloid leukaemia, acute lymphoblastic leukaemia, others
- Other bone marrow pathologies - e.g. myelodysplastic syndrome, CML, CMML, myelofibrosis
- Acute stress - sepsis, haemorrhage, shock
- G-CSF administration
Examples
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