 The French @-@ American @-@ British ( FAB ) classification system divides AML into eight subtypes , <unk> through to <unk> , based on the type of cell from which the leukemia developed and its degree of maturity . This is done by examining the appearance of the malignant cells with light microscopy and / or by using cytogenetics to characterize any underlying chromosomal abnormalities . The subtypes have varying <unk> and responses to therapy . Although the WHO classification ( see above ) may be more useful , the FAB system is still widely used . 
