As ALL is not a solid tumour, the TxNxMx notation as used in solid cancers is of little use.
The FAB classification
Subtyping of the various forms of ALL used to be done according to the French-American-British (FAB) classification, which was used for all acute leukemias (including acute myelogenous leukemia, AML).
- ALL-L1: small uniform cells
- ALL-L2: large varied cells
- ALL-L3: large varied cells with vacuoles (bubble-like features)
Each subtype is then further classified by determining the surface markers of the abnormal lymphocytes, called immunophenotyping. There are 2 main immunologic types: pre-B cell and pre-T cell. The mature B-cell ALL (L3) is now classified as Burkitt's lymphoma/leukemia. Subtyping helps determine the prognosis and most appropriate treatment in treating ALL.
WHO proposed classification of acute lymphoblastic leukemia
The recent WHO International panel on ALL recommends that the FAB classification be abandoned, since the morphological classification has no clinical or prognostic relevance. It instead advocates the use of the immunophenotypic classification mentioned below.
1- Acute lymphoblastic leukemia/lymphoma Synonyms:Former Fab L1/L2
- i. Precursor B acute lymphoblastic leukemia/lymphoma. Cytogenetic subtypes:
- t(12;21)(p12,q22) TEL/AML-1
- t(1;19)(q23;p13) PBX/E2A
- t(9;22)(q34;q11) ABL/BCR
- T(V,11)(V;q23) V/MLL
- ii. Precursor T acute lymphoblastic leukemia/lymphoma
2- Burkitt's leukemia/lymphoma Synonyms:Former FAB L3
3- Biphenotypic acute leukemia
Variant Features of ALL
- 1- Acute lymphoblastic leukemia with cytoplasmic granules
- 2- Aplastic presentation of ALL
- 3- Acute lymphoblastic leukemia with eosinophilia
- 4- Relapse of lymphoblastic leukemia
- 5- Secondary ALL
Immunophenotyping in the diagnosis and classification of ALL
The use of a TdT assay and a panel of monoclonal antibodies (MoAbs) to T cell and B cell associated antigens will identify almost all cases of ALL.
Immunophenotypic categories of acute lymphoblastic leukemia (ALL)
| Types | FAB Class | Tdt | T cell associate antigen | B cell associate antigen | c Ig | s Ig |
|---|
| Precursor B | L1,L2 | + | - | + | -/+ | - |
| Precursor T | L1,L2 | + | + | - | - | - |
| B-cell | L3 | - | - | + | - | + |
Further Reading
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"Acute lymphoblastic leukemia"
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