What is the French-American-British (FAB) classification of acute lymphoblastic leukemia (ALL)?

Updated: Oct 26, 2020
  • Author: Karen Seiter, MD; Chief Editor: Emmanuel C Besa, MD  more...
  • Print
Answer

The older, traditional classification of acute lymphoblastic leukemia (ALL) is the French-American-British (FAB) classification. This has now been replaced by the newer World Health Organization (WHO) classification but the FAB system is listed for historical purposes, as follows:

  • L1 – Small cells with homogeneous chromatin, regular nuclear shape, small or absent nucleolus, and scanty cytoplasm; subtype represents 25-30% of adult cases

  • L2 – Large and heterogeneous cells, heterogeneous chromatin, irregular nuclear shape, and nucleolus often large; subtype represents 70% of cases (most common); see the image below

  • L3 – Large and homogeneous cells with multiple nucleoli, moderate deep blue cytoplasm, and cytoplasmic vacuolization that often overlies the nucleus (most prominent feature); subtype represents 1-2% of adult cases

Acute lymphoblastic leukemia (ALL): Bone marrow shows proliferation of large and heterogeneous lymphoblasts consistent with pre–B-cell ALL (French-American-British L2 morphology).

Acute lymphoblastic leukemia (ALL): Bone marrow sh Acute lymphoblastic leukemia (ALL): Bone marrow shows proliferation of large and heterogeneous lymphoblasts consistent with pre–B-cell ALL (French-American-British L2 morphology).

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!