Leukemia acute
Acute lymphoblastic leukemia (ALL)
ALL - WHO classification

Topic Completed: 1 February 2013

Revised: 20 November 2019

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PubMed Search: WHO classification [title] Acute lymphoblastic leukemia

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Cite this page: Mihova D. ALL - WHO classification. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/leukemiaALLclass.html. Accessed April 3rd, 2020.
Definition / general
  • WHO classification system includes former FAB classifications ALL-L1 and L2
  • FAB L3 is now considered Burkitt lymphoma
WHO classification of acute lymphoblastic leukemia
    Precursor B lymphoblastic leukemia / lymphoblastic lymphoma:
  • ALL with t(9;22)(q34;q11.2); BCR-ABL (Philadelphia chromosome)
  • ALL with t(v;11q23) (MLL rearranged)
  • ALL with t(1;19)(q23;p13.3); TCF3-PBX1 (E2A-PBX1)
  • ALL with t(12;21)(p13;q22); ETV6-RUNX1 (TEL-AML1)
  • Hyperdiploid > 50
  • Hypodiploid
  • t(5;14)(q31;q32); IL3-IGH

Precursor T lymphoblastic leukemia / lymphoma

Additional references
FAB classification of acute lymphoblastic leukemia
  • Terminology now considered to not be relevant because L1 and L2 morphology do not predict immunophenotype, genetic abnormalities or clinical behavior
  • L1: small cells, scant basophilic cytoplasm with variable vacuoles, small nucleoli, regular nuclear shape and homogenous chromatin
  • L2: large heterogeneous cells with moderate cytoplasm, often intensely basophilic, variable vacuoles; large nucleoli, irregular nuclear shape with clefting and indentation, large nucleoli and variable nuclear chromatin
  • L3: medium to large homogenous cells with moderate cytoplasm that is intensely basophilic with prominent cytoplasmic vacuoles; at least one prominent nucleoli (may be 2 - 4), round to oval nucleus, finely stippled homogenous chromatin, cytologically identical to Burkitt and Burkitt-like lymphoma (small noncleaved); has mature phenotype (i.e. expresses surface immunoglobulin); fat vacuoles are Sudan black+, Oil red O+ and PAS-; cytoplasm is methyl green-pyronine positive
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