A 'blast' cell is an early or immature blood cell. Blast cells are important in certain types of cancer that affect the bone marrow, like leukaemia and lymphomas.
Blast cells are very immature or primitive cells. They occur very early in the normal development of white blood cells and disappear very quickly. Normally they are rarely seen in the bone marrow, except at times when it is trying to make more cells than usual, such as when you have an infection or during pregnancy. Blasts are never normally seen in the blood. But, in leukaemia and some types of lymphoma, the marrow can fill up with blast and sometimes they spill out into the blood.
Counting the number of blasts in marrow can help doctors:
- with the diagnosis (for example an acute leukaemia is defined as having 'more than 20% blasts in the marrow')
- to check on how you are responding to treatment (for example, a complete remission is confirmed if there are less than 5% blasts in the marrow).