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Leukemia - Acute

ALL - WHO classification

Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.


● 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

Mod Pathol 2000;13:193

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’s and Burkitt’s 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

End of Leukemia - Acute > ALL - WHO classification

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