Acute Lymphoblastic Leukemia: Background

Unlike the situation in acute myeloid leukemia, in which there are at least eight morphological French-American-British (FAB) subtypes identified by the predominant cell cytology, in acute lymphoblastic leukemia (ALL), there are only three (1 ). Furthermore, for most practical purposes, FAB types L1 and L2 are almost indistinguishable. Of more importance than the morphology of the cells in ALL is the immunophenotype. Apart from identifying an entirely separate T-cell type of ALL, immunology is able to identify cells at various stages of B-cell lineage maturation, including pro-B, pre-pre-B, pre-B, common (cALL), and mature B stages. The last stage constitutes FAB type L3, which has a very close affinity with Burkitt lymphoma; these two disorders share identical cytogenetic abnormalities and both are now formally termed Burkitt cell lymphoma (BL).