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French-American-British classification of acute leukemias based on the study of microscopic features and cytochemistry of blast cells; it subdivides acute myelogenous leukemias into 8 groups (M0-M7) and acute lymphoblastic leukemias into 3 groups (L1-L3); widely used in clinical practice.
Synonym(s): French-American-British classification
(French-American-British) a classification of acute leukemia produced by a three-nation joint collaboration. Acute lymphoblastic leukemia is subdivided into three types and acute myelogenous leukemia is subdivided into eight types.
FAB classificationFrench-American-British classification of acute leukemia Hematology A schema that divides acute leukemias into lymphoid–ALL or myeloid–AML cell lines; of childhood ALL, 70% are predominantly L1, 27% are L2, and 3% or less are L3 or Burkitt cell type, in adults with ALL, 30% are L1, 65% are L2, and 5% are L3
FAB classification, acute leukemias
Acute lymphocytic leukemia (ALL)
L1 Small monotonous lymphocytes
L2 Mixed L1- and L3-type lymphocytes
L3 Large homogeneous blast cells
Acute myeloid leukemia (AML)
M1 Myeloblasts without maturation
M2 Myeloblasts with maturation (best AML prognosis)
M3 Hypergranular promyelocytic leukemia (faggot cells)
M3V Variant, microgranular promyelocytic leukemia
M4 Myelomonocytic leukocytes
M5 Monocytic, subtype
a. Poorly differentiated monocytic leukemia
b. Well differentiated monocytic leukemia
M6 Erythroleukemia/DiGuglielmo syndrome
M7 Megakaryocytic leukemia Pleomorphic undifferentiated cells with cytoplasmic blebs; myelofibrosis or ↑ BM reticulin; positive for platelet peroxidase antifactor VIII