What is the WHO classification of acute lymphoblastic leukemia (ALL)?

Updated: Jul 02, 2021
  • Author: Karen Seiter, MD; Chief Editor: Emmanuel C Besa, MD  more...
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In 2016 the World Health Organization Classification publicised a revised classification of ALL [21] . This classification included 2 new provisional entities for B-ALL. The first, B-lymphoblastic leukemia/lymphoma, BCR-ABL1-like, was originally reported as a subtype of poor prognosis childhood ALL with a gene expression profile similar to Philadelphia chromosome positive ALL [22, 23] . Some cases of this subtype of ALL respond to therapy with tyrosine kinase inhibitors. The second,  B-ALL with intrachromosomal amplification of chromosome 21, is characteristically detected by FISH with a probe for RUNX1 that reveals 5 or more copies of the gene [24, 25] . The latter subtype occurs in older children with low WBC and is associated with a poor prognosis. Currently there is no subdivision of T-ALL with the exception of two new provisional subtypes. Early T-cell precursor lymphoblastic leukemia is a subtype with only limited early T-cell differentiation with retention of some myeloid and stem cell characteristics [26, 27] . The prognosis of this subtype is variable from report to report. Natural killer cell lymphoblastic leukemia/lymphoma is another newly described subtype .

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