13 November 2024 (Wednesday) - Spot the Difference

Had an interesting conversation today which made me think. What *exactly* is the difference between a myelocyte and a promyelocyte?
They can be rather tricky to tell apart…
So I’ve had a think and done some Googling…
 
  • Promyelocytes are bigger.
  • Promyelocytes have prominent nucleoli and Golgi apparatus.
  • Myelocytes do not have nucleoli and Golgi apparatus.
  • Compared to the myelocyte, much more of the promyelocyte is nucleus
  • Promyelocytes have huge, dark purple, primary (azurophilic) granules both in the cytoplasm and overlying the nucleus.
  • Promyelocytes do NOT have secondary (specific,to neutrophil, eosinophil or basophil) granulation – not even the beginnings of it!  If you see any of that secondary granulation (even just a little blush of it in the cytoplasm) then it’s a myelocyte. The promyelocytes of the three granulocytic lineages cannot be distinguished by routine light microscopy.

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