What is Leukemia?
Leukemias are due to proliferation of malignant blast cells.
Malignancy of blood-forming tissue, typically the white blood cells.
From Greek: “leuk” = white “emia” = blood
“Blast”refers to a malignant leukemia cell
However, normal bone marrow can have a few normal blasts that are not malignant.
- Under 5% blasts can be normal
- Leukemia has by definition > 25% blasts at diagnosis.
The diagram below shows the normal development of the different blood cell lines from bone marrow stem cells:
Blasts in leukemia:
- Fail to mature but keep replicating and dividing
- Crowd out the normal cells
- Appear “Monomorphic” - all cells look similar
Bone marrow aspirate in ALL (the purple cells are leukemic blast cells):