Acute leukaemia I: classification and diagnosis


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Acute leukaemia is a malignant disorder in which haemopoietic blast cells constitute >20% of bone marrow cells. The primitive cells usually also accumulate in the blood, infiltrate other tissues and cause bone marrow failure.




Classification


There are two main groups: acute lymphoblastic (ALL) and acute myeloid (myeloblastic) leukaemia (AML). Rare cases are undifferentiated or mixed. Subclassification of ALL or AML depends on morphological, immunological, cytogenetic and molecular criteria (Boxes 22.1 and 22.2; Table 22.1).







Box 22.1 World Health Organization (WHO) 2008 classification of acute leukaemia (simplified)


AML

AML with recurrent cytogenetic abnormalities



AML with t(8,21) (AML1/ETO)

Acute promyelocytic leukaemia with t(15,17) (PML/RARA)

AML with abnormal bone marrow eosinophils with inv 16 (CBFβ/MYH11)

AML with 11q23 (MLL) abnormalities

AML with other cytogenetic abnormalities

AML with myelodysplasia-related features


Therapy-related myeloid neoplasms


AML with mutated NPMI or CEBPA


AML not otherwise categorized



AML with minimal differentiation

AML without maturation

AML with maturation

Acute myelomonocytic leukaemia

Acute monoblastic and monocytic leukaemia

Acute erythroid, erythroid/myeloid, megakaryoblastic/basophilic leukaemia

Acute leukaemia of ambiguous lineage (undifferentiated or biphenotypic)



ALL

Precursor B-cell lymphoblastic leukaemia/lymphoma



Unspecified

With recurrent cytogenetic/molecular genetic abnormalities, e.g. t(9;22), t(v;11q23), t(12;21), hyperdiploidy, hypodiploidy, t(1;19)

Precursor T-cell lymphoblastic leukaemia/lymphoma


ALL, acute lymphoblastic leukaemia; AML, acute myeloid leukaemia


NB The WHO classification also includes myeloid proliferations related to Down’s syndrome which may be transient











Box 22.2 Prognostic indicators in acute myeloid leukaemia


Good risk

Cytogenetic changes: (8,21), t(15,17), inversion 16


Remission after course 1 of chemotherapy is also a favourable feature



Poor risk

Cytogenetic changes: monosomy 5; monosomy 7; complex karyotypes, 11q 23 abnormalities


Age over 70 years is also unfavourable


Jun 12, 2016 | Posted by in HEMATOLOGY | Comments Off on Acute leukaemia I: classification and diagnosis

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