Cytochemical and immunological aspects of the acute lymphocytic leukemias (as related to FAB classification).

The FAB classification of acute leukemias was proposed by a cooperative French-American-British group as an easily applied classification useful for uniform assessment of large clinical therapeutic trials. Although the classification is based on morphological criteria, cytochemical, biochemical, immunological and cytogenetic studies supplement the morphologic criteria for accurate identification of the leukemic blasts. The FAB criteria are shown by these supplementary studies to be deficient for classifying the acute lymphocytic leukemias (ALL) since various subgroups of ALL appear in more than one FAB group. Precise definitions of clinical-pathological entities within the framework of the FAB classification are desirable.