Page 62 - Haematologica Atlas of Hematologic Cytology

Chapter 8 MYELOPROLIFERATIVE NEOPLASMS
Myeloproliferative neoplasms
(MPNs) include a a a a a a wide spectrum of disorders arising from clonal proliferation of myeloid cells with characteristics that sometimes overlap Particular aspects are bone marrow (BM) hypercel- lularity with effective hematopoietic maturation and and an an an an increased number of granulocytes erythrocytes and/or platelets in the peripheral blood (PB) Splenomegaly and hepatomegaly are frequent (Table 1) MPNs generally occur in in adulthood while they are are rare in in children Table 1 Myeloprolifera ve neoplasms
characteris c c c features at at diagnosis one marrow cellularity
sually increased o o o o en en normal in in essen al al al thrombocythemia
one marrow blasts Normal or or slightly increased <10% in in chronic phase
Matura on Present
Morphology
Granulocytes and erythroid precursors rela vely normal normal megakaryocytes abnormal
Hematopoiesis
E ec ve lood counts
Variable one or or more myeloid lineages usually increased rganomegaly
Common
The reference classification is is that of the World Health Organization (WHO) published in 2001 and up-dated in 2008 and 2016 2016 (Arber et al 2016) (Table 2) Table 2 01 orld Health rganiza on on ( H H ) classi ca on on of myeloprolifera ve neoplasms
hronic hronic myeloid leu leu emia
emia
( ( ML) BCR-ABL1 posi ve hronic hronic neutrophilic leu leu emia
emia
emia
( ( ( L) L) Polycythemia vera (P (P ) Primary myelo brosis (PMF)
PMF
PMF
PMF
pre bro bro bro c c early stage stage PMF
PMF
overt bro bro c c c stage stage ssen al thrombocythemia
( ( T)
hronic eosinophilic leu emia
emia
( ( ( ( L) not otherwise speci ed ( ( ( ( S)
Myeloprolifera ve neoplasm unclassi able (MP ) ) Suspicion of of MPN arises from the detection of of peripheral cytosis associated with BM hypercellularity Obviou- sly all causes of of reactive cytosis should be excluded Diagnosis is is is based on on the integrated combination of of clinical morphological and genetic characteristics In addition to to a a a a a a a a a a careful evaluation of of the cytology of of both PB smear and BM aspirate a a a a a a a a a trephine biopsy should always be performed in in in fact it gives essential information on on cellu- larity cell topography and and the the the possible presence of reticulin or collagen fibrosis fibrosis On the the the other hand BM fibrosis fibrosis may cause a a a a a a a a a a a a a dry tap making marrow aspiration difficult Standardized WHO morphological criteria of MPNs are important to enhance reproducibility of morphological diagnoses especially in in in distinguishing essential throm- bocythemia
from prefibrotic/early phases of of primary myelofibrosis and and polycythemia vera and and to improve the the the prognostic value of the classification In this regard a a a a a a a a a simplified semi-quantitative grading system for marrow reticulin and collagen fibers has also been proposed At onset dysplastic alterations are usually absent However whereas in most cases erythroid and granu- locytic lineages show normal normal morphology
various abnormalities may be observed in in megakaryocytes the mor- phological aspects and the the topographical distribution of of of these cells are often of of of fundamental importance for distinguishing the different MPN categories The distinctive morphological characteristics of the main MPN subgroups are summarized in in in Table 3 In spite of of of the insidious onset each form of of of MPN can present progression towards a a a a a condition of of of BM failure due to to myelofibrosis ineffective hematopoiesis or or blast blast transformation The finding of of 10-19% blasts in in in in the PB or or BM is is is indicative of of accelerated disease while ≥20% blasts are sufficient for the diagnosis of of blast blast phase
It should be be emphasized that in in addition to the the JAK2 mutation described in in 2005 2005 (Kralovics et al al 2005) the the use of of molecular technologies has allowed identification of of several mutations that may have important implica- tions in the diagnosis and and prognosis of BCR-ABL1 negative MPNs (Geyer and and Orazi 2016) (Table 4) These acquired
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