CLINICAL NEWS
classically associated with bi-allelic, but
not single, mutations of the gene and
has resulted in a change in the definition to require the presence of biallelic
mutations. Due to the lack of prognostic
significance of multilineage dysplasia
in patients without MDS-associated
cytogenetic findings and with a mutation
of NPM1 or biallelic mutation of CEBPA,
these mutations now supersede the
presence of multilineage dysplasia in the
classification.
In addition, a provisional category of
AML with mutated RUNX1 has been added
to the classification for de novo AML.
Under the classification for AML, not
otherwise specified, the subcategory of acute
erythroid leukemia, erythroid/myeloid type
(previously defined as having ≥50% bone
marrow erythroid precursors and ≥20%
myeloblasts among non-erythroid cells)
has been removed. Myeloblasts are always
counted as a percentage of total marrow
cells, with the majority of these cases having less than 20 percent total blast cells,
thus classified as MDS.
Acute Leukemias of Ambiguous
Lineage
Preliminary data suggest that mixed
phenotype acute leukemia with t(9;22)
respond favorably to TKI treatment.
New provisions have been added for
B-cell lymphoblastic leukemia/lymphoma
(B-ALL) and T-cell lymphoblastic leukemia/lymphoma (T-ALL). For B-ALL, two
provisional entities with recurrent genetic abnormalities have been recognized:
• B-ALL with intrachromosomal amplification of chromosome 21
»»Amplification of a portion of chromosome 21
»»Occurs in about 2% of children with
ALL, especially older children with
low WBC counts
»»Associated with an adverse prognosis,
which, to some extent, can be overcome with more aggressive therapy
• B-ALL with translocations involving
tyrosine kinases or cytokine receptors
»»Associated with an adverse prognosis
and responses of some cases to TKIs
»»Difficult to define in the clinical setting
Though studies have investigated the genetic mechanisms of T-ALL, assays have
not yet been standardized and prognostic
implications are still controversial.
REFERENCES
1. Arber DA, Orazi A, Hasserjian R, et al. The