The classification of acute leukaemia in childhood.

In 1976 a French, American and British (FAB) cooperative group proposed a morphological classification of acute leukaemia which they hoped would prove more reproducible than previous classification. We present our preliminary experience with this classification, based on a 2-year study of 39 patients. Cytochemical and cell surface marker characteristics of the leukaemic cells were also studied. We found this classification to be satisfactory but some problems were noted in regard to its reproducibility, especially in acute lymphoblastic leukaemia (ALL). Cell surface markers were absent in the majority of cases of ALL ("null cell" type), while the remainder had T-cell characteristics. No B-cell types were seen. Cytochemical staining patterns clearly distinguished ALL from acute myeloid leukaemia (AML) and also helped to categorize AML into its subtypes. The implications of our finding are discussed.