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Diagnosis and classification of the acute leukemias: recent advances and controversial issues
C G Taylor1, R Stasi, C Bastianelli
1Division of Haematology, Pembury Hospital, Kent, U.K.
Insights
Advances in biotechnology, including immunophenotyping, cytogenetics, and molecular analysis, enhance the diagnosis and classification of acute leukemia (AL). These methods offer deeper insights into distinct clinico-biologic features, improving patient management and challenging traditional classifications.
Area of Science:
- Hematology and Oncology
- Molecular Biology
- Biotechnology
Background:
- Traditional morphology and cytochemistry are mainstays for acute leukemia (AL) diagnosis.
- New biotechnological advancements offer improved understanding and identification of distinct AL subtypes.
- Existing classifications may not fully integrate new diagnostic information.
Purpose of the Study:
- To review recent diagnostic contributions in acute leukemia (AL) stemming from biotechnology.
- To discuss the impact of new diagnostic tools on understanding and classifying AL.
- To highlight controversies in current AL classification systems.
Main Methods:
- Immunophenotyping for diagnosing and subclassifying acute lymphoblastic leukemia (ALL) and certain acute myeloid leukemias (AML).
- Cytogenetic analysis to identify clinically relevant chromosomal abnormalities for diagnosis and prognosis.
- Molecular analysis to assess malignant potential, clonality, and classification, identifying molecular defects independent of karyotype.
- In vitro assays to evaluate leukemic cell growth, cell-cycle kinetics, and sensitivity to therapeutic agents.
Main Results:
- Immunophenotyping is crucial for ALL and helpful in specific AML subtypes.
- Specific nonrandom chromosomal abnormalities (e.g., t(15;17)) can aid in diagnosis.
- Molecular analysis reveals distinct genetic profiles and can identify disease even without karyotypic changes.
- In vitro assays provide data relevant to AL management.
Conclusions:
- Biotechnological advances significantly enhance the diagnosis, subclassification, and understanding of acute leukemias.
- These new data necessitate a re-evaluation of existing classification systems.
- Further research and discussion are needed to resolve classification controversies.
Abstract:
Although morphology and cytochemistry continue to be the mainstay of the diagnosis of acute leukemia (AL), new developments in immunophenotyping, cytogenetics, molecular biology, and in vitro assays have dramatically improved our understanding of this disease and enabled the identification of entities with distinct clinico-biologic features. Immunophenotyping is essential for diagnosing and subclassifying acute lymphoblastic leukemia (ALL) and is also very helpful in certain types of acute myeloid leukemias (AML), such as AML with minimal differentiation or acute megakaryoblastic leukemia. Cytogenetic findings are clinically relevant for diagnosis and prognosis. Nonrandom chromosomal abnormalities such as t(15;17)(q22;q12) or t(1;19)(q23;p13) have been so closely associated with distinct types of acute leukemias that their recognition can allow diagnosis independent of the other criteria. Molecular analysis is a powerful method in the assessment of the malignant potential, clonality, and classification of the ALs. It has become clear that in some leukemias a proportion of patients exhibit the biologically relevant molecular defect in the absence of a karyotypic equivalent. On the other hand apparently uniform chromosomal abnormalities such as the t(1;19), t(9;22), t(8;14), or t(15;17) may differ at the molecular level. In vitro assays can evaluate the growth pattern and cell-cycle kinetics of leukemic cells, as well as their sensitivity to therapeutic agents. All these data are relevant to the management of AL. Because the French-American-British (FAB) classification does not fully correlate with much of this new information, alternative classifications have been proposed. In this review we concentrate on recent diagnostic contributions resulting from advances in biotechnology and discuss some of the points that arouse controversy in the single classifications.