Myeloperoxidase(MPO): Must know facts!!!! #Medschooldiscussion

Myeloperoxidase or MPO is an enzyme located in the primary or azurophilic granules of myeloid cells. MPO positivity appears as coloured granules in the cytoplasm of cells mainly at the site of enzyme activity that is golgi zone.The coloured granules are brown or slightly blackish in colour.
All the stages of neutrophil series show MPO positivity.Even in AML M0 blast peroxidase activity can be demonstrated by electron microscopy!!!! Promyelocyte and myelocyte are the most strongly stained cells in the granulocyte series. Metamyelocytes and neutrophils have relatively fewer positive granules.
MPO is positive in AML subtypes M0,M1,M2,M3 and M4 and this positivity helps in diagnosis of these leukaemias.
Monoblasts or monocytes may be MPO positive but the granules are smaller than in neutrophils and these granules are diffusely scattered throughout the cytoplasm.
Sometimes MPO positivity is found in eosinophils and its precursors. But the MPO in eosinophil granules is cyanide resistant, whereas that in neutrophils and monocytes is cyanide sensitive.
Red cells and erythroid precursors show diffuse brown cytoplasmic staining.
But interestingly MPO is never seen in lymphoblasts!!!
That is why the main use of MPO is to distinguish AML from ALL.The blasts in AML SHOW GRANULAR POSITIVITY while the blasts in ALL are negative for MPO.
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[TheMedsick]

Good video do continue ...
Expecting more videos from u sir