Classification systems for acute and chronic leukaemias.

Area of Science:

• Hematology
• Oncology
• Molecular Diagnostics

Background:

• Current leukaemia classification relies on cytomorphology, cytochemistry, and immunophenotyping.
• While morphology is initial, it's insufficient for identifying biologically relevant leukaemic subsets.
• Immunophenotyping precisely defines cell lineage and differentiation stage, crucial for lymphoid malignancies.

Purpose of the Study:

• To summarize and comment on current immunophenotypic classification systems for acute and chronic leukaemias.
• To highlight the added value of molecular diagnostics in leukaemia classification.
• To discuss the integration of new criteria, such as gene expression profiling, into future classifications.

Main Methods:

• Review of current diagnostic techniques including morphology, immunophenotyping, immunogenetics, and molecular cytogenetics.
• Analysis of the limitations of morphology and immunophenotyping in classifying heterogeneous leukaemias.
• Discussion of the role of cytogenetic and molecular studies in identifying leukaemogenic events and chromosome aberrations.

Main Results:

• Immunophenotyping is essential for precise classification, especially in lymphoid malignancies.
• Acute leukaemias remain heterogeneous despite cytomorphology and immunophenotyping, necessitating further molecular investigation.
• Combined diagnostic information, including molecular data, forms the basis of the WHO classification.

Conclusions:

• Integrated diagnostic approaches combining morphology, immunophenotyping, and molecular studies are vital for accurate leukaemia classification.
• Molecular diagnostics significantly enhance the ability to identify specific leukaemic subgroups and underlying genetic abnormalities.
• Future classifications will likely incorporate novel data from microarray gene expression profiling for more refined diagnoses.