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Haematological classification of the chronic myeloid leukaemias
Insights
Chronic myeloid leukaemia (CML) encompasses five subtypes, with chronic granulocytic leukaemia being the most common. Diagnosis of most CML subtypes relies on peripheral blood film morphology and staining.
Area of Science:
- Hematology
- Oncology
- Leukemia Research
Background:
- Chronic myeloid leukaemia (CML) is a heterogeneous group of related myeloid disorders.
- CML comprises five distinct subtypes, each with unique characteristics and prevalence.
- Accurate classification is crucial for understanding disease progression and patient outcomes.
Purpose of the Study:
- To delineate the five subtypes of Chronic Myeloid Leukaemia (CML).
- To highlight the diagnostic criteria and relative frequencies of each subtype.
- To emphasize the importance of morphological analysis in CML diagnosis.
Main Methods:
- Review and synthesis of existing literature on CML classification.
- Analysis of morphological features in peripheral blood films for diagnosis.
- Consideration of cytogenetic markers (Ph, BCR) in subtype identification.
Main Results:
- CML subtypes include Chronic Granulocytic Leukaemia (CGL, 95%), Juvenile CML, Chronic Neutrophilic Leukaemia (CNL), Chronic Myelomonocytic Leukaemia (CMML), and Atypical CML (aCML).
- CGL is predominantly Ph+, BCR+, while other subtypes are typically Ph-, BCR-.
- CMML classification depends on leukocyte count, distinguishing myelodysplastic from myelodysplastic/myeloproliferative conditions.
- Atypical CML exhibits features intermediate between CGL and CMML with worse survival.
- Subtypes 2, 3, 4, and 5 constitute approximately 5% of all CML cases.
Conclusions:
- CML classification into subtypes is essential for clinical management.
- Morphological examination of peripheral blood films is a primary diagnostic tool for most CML subtypes.
- Further refinement of definitions, particularly for aCML, is warranted.
Abstract:
Chronic myeloid leukaemia (CML) includes five subtypes, and the term should be used in the same way as the term chronic lymphoid leukaemia to refer to a group of related conditions. The subtypes of CML are: 1. Chronic granulocytic leukaemia (CGL) (95% of all CML; 90% are Ph+, BCR+, 5% are Ph-, BCR+); 2. Juvenile CML (extremely rare; Ph-, BCR- in the few so far examined); 3. Chronic neutrophilic leukaemia (CNL) (extremely rare; Ph-, BCR- in the few so far examined); 4. Chronic myelomonocytic leukaemia (CMML). CMML with low or normal leukocyte counts is classified as a myelodysplastic syndrome; CMML with high leukocyte count is both myelodysplastic and myeloproliferative. Ph-, BCR-; 5. Atypical CML (aCML). Intermediate between CGL and CMML but has distinctive features. Ph-, mostly BCR-. Significance of few reported BCR+ uncertain. Markedly worse survival than CGL and probably worse than CMML. Definition needs refining. Types 2, 3, 4 and 5 account for 5% of all CML. CGL, CMML, aCML and CNL can be diagnosed in the great majority of cases from the morphological profile of presentation peripheral blood films, but high-quality Romanowsky staining is essential.