Page 81 - Haematologica Atlas of Hematologic Cytology

CHAPTER 11 - Myelodysplastic/myeloproliferative neoplasms
Chapter 11. MYELODYSPLASTIC/MYELOPROLIFERATIVE NEOPLASMS
Myelodysplastic/myeloproliferative neoplasms (MDS/MPNs) are myeloid neoplasms that at initial presenta- tion have some clinical, laboratory or morphological findings supporting the diagnosis of myelodysplastic syn- drome (MDS), whereas other findings are more consistent with the diagnosis of myeloproliferative neoplasm (MPN). The marrow is normal or hypercellular due to the proliferation of one or more myeloid lineages. While proliferation is effective in some lineages with increased numbers of circulating cells, in one or more of the other lineages proliferation may be ineffective with peripheral cytopenia (Table 1).
Table 1. Myelodysplastic/myeloproliferative neoplasms: characteristic features at diagnosis
WBC: white blood cell
According to the World Health Organization (WHO) classification published in 2001 and up-dated in 2008 and 2016 (Arber et al., 2016), this category of disorders includes the following entities: chronic myelomonocytic leukemia (CMML), atypical chronic myeloid leukemia (aCML), BCR-ABL1 negative, uvenile myelomonocytic leu- kemia (JMML), myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/ MPN-RS-T), and myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U). The morphological diagnostic criteria of these entities are summarized in Table 2.
Correct identification of monocytic cells is crucial for differential diagnosis. The different maturation stages of monocytic cells have been defined by the International Working Group on Morphology of Myelodysplastic Syndrome (IWGM-MDS) (Goasguen et al., 2009).
Table 2. Morphological features of myelodysplas c/myeloprolifera ve neoplasm subtypes.
Bone marrow cellularity
Increased
% bone marrow blasts
Normal or slightly increased; <20%
Matura on
Present
Morphology
sually one or more lineages dysplas c; uvenile chronic myelomonocy c leukemia o en has minimal dysplasia
Hematopoiesis
Ine cacy may vary among lineages
Blood counts
Variable, WBC usually increased
Organomegaly
Common
Peripheral blood
Bone marrow
Monocytes
Neutrophil precursors
Blasts*
Dysplasia
Blasts*
CMML
>1 x 109/L** and >10%
<10%
<20%
Variable
<20%
CMML-0
<2%
<5%
CMML-1
2-4%
5-9%
CMML-2
5-19%
10-19% or Auer rods
aCML
<10%
>10% and WBC >13 x 109/L
<20%
Granulocy c + mul lineage
<20%
JMML
>1 x 109/L
Usually present
<20%
Minimal
<20%
MDS/MPN-RS-T°
Very rare
<1%
Erythroid (>15% ring sideroblasts) + mul lineage
<5%
*Including promonocytes ** Persistent for ≥ 3 months Persistent thrombocytosis ≥450 x 109/L. CMML, chronic myelomonocy c leukemia; aCML, atypical chronic myeloid leukemia; JMML, uvenile myelomonocy c leukemia; MDS/MPN-RS-T, myelodysplas c myeloprolifera ve neoplasm with ring sideroblasts and thrombocytosis; WBC: whi- te blood cell
Promonocytes differ from monoblasts for their irregular nuclear outline but have a similar immature chroma- tin pattern; they are blast equivalent and should be counted as such. Atypical/immature monocytes are characte- rized by a more condensed chromatin pattern and less evident nucleoli, but it can be very difficult to distinguish
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