TRAINING and EDUCATION
How I Treat In Brief
Recently, David P. Steensma, MD, of Dana-Farber Cancer Institute and Harvard Medical School in Boston, discussed
how to use results from molecular genetic tests in the diagnosis and evaluation of patients with myelodysplastic
syndromes. Below, we summarize his approach.
This material was repurposed from “How I use molecular genetic tests to evaluate patients who have or may
have myelodysplastic syndromes,” published in the October 18, 2018, issue of Blood.
Using Molecular Genetic Tests to Evaluate
Myelodysplastic Syndromes
Myelodysplastic syndromes (MDS) are defined
by the presence of persistent blood cytopenias
associated with certain characteristic morphologic
changes in blood and marrow cells. However, none
of these morphologic findings is specific for MDS
and the assessment of dysplasia is to some extent
subjective. Therefore, to diagnose MDS, the 2016
World Health Organization (WHO) classification
continues to require finding >10 percent dysplastic
cells in more than one hematopoietic lineage, an
abnormal karyotype, or an increase in myeloblasts
( TABLE ).
In the past 10 years, though, researchers
have discovered more than 40 recurrent, MDS-
associated gene mutations. This has raised hope
that molecular genetic testing for these mutations
might help clarify the diagnosis in ambiguous
cases where patients present with cytopenias and
nondiagnostic marrow morphologic findings.
Next-generation sequencing (NGS) assays that
test for subsets of these MDS-associated gene mu-
tations at the DNA level are now widely available in
clinical practice and are frequently employed in di-
agnostic evaluation. As a hematology community,
however, we are still learning how best to use these
assays, both for the evaluation of patients with
cytopenias who might have MDS and in patients
with established MDS.
The following four cases illustrate some of the
potential benefits and challenges related to the use
of molecular genetic testing in clinical practice.
Case #1: Ruling out a Clonal Disorder
A 72-year-old woman was found to have macro-
cytic anemia after she saw a new primary-care
physician and mentioned increased fatigue.
Her white blood cell (WBC) count and absolute
neutrophil count were within normal limits, and
the blood smear showed no abnormal leukocytes.
There was no obvious explanation for her cytope-
nias based on her medications or basic laboratory
studies, including serum chemistries, vitamin
B 12 and red cell folate levels, and a serum protein
electrophoresis.
Her primary-care physician requested that a
marrow aspiration and biopsy be performed. Mar-
row morphology was nondiagnostic: 30 percent
cellular (normocellular for age), with only rare
dysplastic megakaryocytes representing <10
percent of cells in that lineage. Flow cytometry
was reported as unremarkable, and
the karyotype was normal female
metaphase in 20 metaphases.
TABLE. Proposed Minimal Diagnostic Criteria
A 95-gene NGS panel showed no
for MDS
pathogenic single nucleotide vari-
Diagnosis of MDS requires:
ants or small insertions/deletions and
read count analysis showed no copy
(A) Persistent blood cytopenia(s) as defined by local laboratory ranges
(with consideration of patient factors, such as ethnic background,
number alterations. The patient was
altitude of residence, etc.), without another reversible cause, such as
told that she had idiopathic cytopenia
nutritional deficiency or the effect of a drug, and
of undetermined significance (ICUS),
(B1) Increased myeloblasts (5-19%), or
and observation was recommended.
(B2) Extensive dysplasia (>10% of marrow cells in at least 1 lineage:
erythroid, granulocytic, or megakaryocytic), or
(B3) Karyotypic evidence of clonality with a typical MDS-associated
alteration, such as del(5q) or monosomy 7 (excluding nonspecific
alterations, such as trisomy 8, loss of the Y chromosome, isolated
del20q, or trisomy 1553)
Supplemental “co-criteria” include:
(C1) Abnormal findings on histologic or immunochemical studies
of marrow biopsy that could be consistent with MDS, such as
abnormally localized immature precursors, clusters of CD34-positive
blast cells, or >10% dysplastic micromegakaryocytes detected by
immunohistochemistry
(C2) Abnormal immunophenotype of marrow cells by flow cytometry
with multiple MDS-associated phenotypic aberrancies
(C3) Evidence of a clonal population of myeloid cells by molecular
genetic testing, which is the subject of this article
If (A) is present, but not (B1-B3), then the case might be termed
“idiopathic cytopenias of undetermined significance” (ICUS), a term
that is agnostic about clonality.
C1-C3 alone are generally not yet considered specific enough by
themselves to be confident about the diagnosis of MDS but can help
confirm the diagnosis if other criteria are present.
Source: WHO 2016 Disease Classification.
ASHClinicalNews.org
Commentary: NGS panels can be use-
ful for helping rule out a clonal disor-
der because they have a relatively high
negative predictive value for MDS.
A small proportion of patients with
MDS will have negative results on an
NGS panel; however, the finding of
a negative result on a well-designed
panel in an ambiguous case such as
this one should prompt consideration
of an alternative diagnosis. In this
case, over time, it became clear that
the patient had excessive alcohol con-
sumption and experienced pathologic
grief after the loss of her husband.
After she was provided appropriate
psychosocial support and discontin-
ued use of alcohol, her blood counts
returned to normal.
It can be argued that a patient like
this one could be followed serially
over time, sparing the expense of an NGS panel
(and of a marrow biopsy). However, especially
for patients with one or more cytopenias, there
is often considerable worry about an evolving
clonal disorder, which may coexist with other
potential causes of cytopenias, including alcohol
use. When NGS panels are used, they must be
interpreted in the context of the information
obtained from morphology and conventional
cytogenetic testing. As NGS panels become less
expensive, it seems likely that they will move
earlier in the diagnostic testing algorithm for
patients with cytopenias.
Case #2: Identifying High-Risk CCUS
A 67-year-old man was referred to our center after
he was found to have macrocytic anemia, which
persisted for nine months and was slightly worse
at the time of initial evaluation. His WBC count
and differential were unremarkable, and his platelet
count was at the lower end of the normal range
(188×10 9 /L). His previous blood counts had been
normal except for mild normocytic anemia noted
at the time of a bacterial pneumonia three years
earlier, which eventually resolved. There were no
medications or comorbid conditions that were felt
likely be contributing to his cytopenias, and he did
not drink alcohol.
In the past 10 years,
researchers have
discovered more
than 40 recurrent,
MDS-associated
gene mutations.
The patient was a physician with extensive pre-
vious exposure to fluoroscopy that raised concern
for an exposure-related MDS, and therefore, he
underwent a bone marrow aspirate and biopsy.
This showed a 40 percent cellular marrow with
rare megaloblastoid or binucleate erythroid cells,
representing <10 percent of nucleated erythroid
precursors. Flow cytometry was unremarkable, and
the karyotype was normal male metaphase in all 20
metaphases tested.
However, a molecular genetic panel showed
a DNMT3A R882H mutation with 14.6 percent
variant allele frequency (VAF). The patient was
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