Histol Histopathol (2019) 34: 857-873 Histology and http://www.hh.um.es FHromi Cseltl Boiolopgya to tTihssuoe Elnogingeerying Review The importance of adequate recognition of normal and dysplastic myelopoiesis for the diagnosis of myelodysplastic syndromes Lourdes Florensa*, Leonor Arenillas*, Xavier Calvo*, Encarnación Pérez-Vila, Sara Montesdeoca, Ana Ferrer and Soledad Woessner Escola de Citologia Hematològica Soledad Woessner-Parc de Salut Mar, Laboratorio de Citología Hematológica, Patología, GRETNHE, IMIM Hospital del Mar Research Institute, Barcelona, Spain *contributed equally to this work. Summary. The diagnosis of myelodysplastic syndromes Key words: Myelodisplastic syndrome, Myelodysplasia, is based on the presence of cytopenias, dysplastic Dyserythropoiesis, Dysgranulopoiesis, Dysmega- morphological features on peripheral blood (PB) and kariopoiesis, Granulopoiesis, Erythropoiesis, bone marrow (BM), cytogenetic abnormalities and Megakaryopoiesis, Mospoiesis, Dysplasia requires to rule out other diseases resembling these conditions. Optical cytomorphology is the cornerstone of diagnosis of MDS. The recognition of cytological Introduction myelodysplasia has a crucial value in diagnosis and prognosis of MDS. Assessment of cytological The 2008 and 2017 WHO Classifications of morphology requires, like other diagnostic techniques Tumours of Haematopoietic and Lymphoid Tissues (flow cytometry, cytogenetics, histological morphology), requires the recognition of dysplastic features for the experienced observers and the availability of high diagnosis of myelodysplastic syndromes (MDS) and quality and properly stained samples. The morphological other myeloid neoplasms. The myelodysplastic analysis has shown moderate reproducibility among syndromes are a group of acquired clonal hematopoietic hematopathologists. The better characterization and stem cell disorders with very heterogeneous outcomes, standardization of morphological features has improved characterized by ineffective hematopoiesis, manifested the reliability and reproducibility of MDS diagnosis. by morphologic dysplasia in hematopoietic cells, Maintaining the competence in morphology assessment peripheral cytopenia(s) and an increased risk of requires experience and continuous training. For the development of acute myeloid leukemia (AML). The correct assessment of cytologic myelodysplasia it is diagnosis of MDS is based on a combination of medical essential to keep in mind the morphology of normal history, morphological features on peripheral blood (PB) myelopoiesis. To the extent of our knowledge there are and bone marrow (BM), cytogenetic and molecular data no studies describing together morphological data on and it is mandatory to rule out other diseases. Optical normal and dysplastic myelopoiesis in the framework of cytomorphology is the cornerstone of diagnosis of MDS. MDS. Therefore, by combining these data, this The recognition of cytological myelodysplasia has a manuscript could serve as a useful tool for quotidian crucial value in diagnosis, classification and prognosis of process of diagnosis. MDS, although the presence of dysplasia is not in itself definitive evidence of a clonal disorder. It is very Offprint requests to: Lourdes Florensa, Paseo Marítimo, 25, 08003 important to consider that myelodysplasia is not Barcelona, Spain. e-mail: [email protected]. synonymous of MDS; no pathognomonic data of MDS DOI: 10.14670/HH-18-093 exist and it is imperative to exclude other causes of 858 Cytomorphology assessment in MDS transient dysplasia (vitamin B12 and folic acid important to remember that the normal maturational deficiency, viral infections, ethanol, exposure to lead and process of myeloid cells is continuous, with a gradual other heavy metals, particularly arsenic and several transition from one stage to the next, and therefore the commonly used antibiotics, drugs and biological agents exact maturation stage of maturation may be difficult to among others (Brunning et al., 2008; Hasserjian et al., establish. To the extent of our knowledge there are no 2017). Such conditions should be ruled out by a careful studies describing together morphological data on clinical history and physical and laboratory normal and dysplastic myelopoiesis in the framework of examinations. The diagnosis of MDS should not be MDS. Therefore, it seemed interesting to gather in single established while the patient is on growth factor therapy, article different images of normal and dysplastic including erythropoietin (Brunning et al., 2008; myelopoiesis (erythroblastic, granulocytic, Hasserjian et al., 2017). Assessment of cytological megakaryocytic, and monocytic lineages) (Bennett et al., morphology requires, like other diagnostic techniques 1982; Woessner and Florensa, 2006; Brunning et al., (flow cytometry, cytogenetics, and histological 2008; Hasserjian et al., 2017). In addition, few morphology), experienced observers and the availability ultrastructural (US) images that may be helpful for the of high quality and properly stained samples (Bennett et understanding of some morphological data have been al., 1984; Brunning et al., 2008; Béné and Zini, 2017; included. Hasserjian et al., 2017). Poor quality smears may result Major manifestations of dysplasia are depicted in misinterpretation which is particularly notorious in (Brunning et al., 2008; Hasserjian et al., 2017) in Table 1. assessing neutrophilic granulation. Slides should be made from freshly obtained specimens (peripheral blood Morphological characteristics of myelopoiesis exposed to anticoagulants for more than two hours is unsatisfactory) (Brunning et al., 2008; Hasserjian et al., General characteristics of normal erythroid differentiation 2017). The morphological analysis requires identification of blast cells in BM and PB, type and During the maturation process we can observe the degree of dysplasia and presence of ring sideroblasts. As following changes: a decrease in cell size, a reduction of defined in the 2008 and 2017 WHO classifications the nucleo-cytoplasmic ratio and a progressive nuclear (Brunning et al., 2008; Hasserjian et al., 2017), for enumeration of the blasts counting at least 200 cells in blood smears and 500 cells in BM smears is required. To assess dysplasia at least 200 neutrophils, 200 erythroid precursors and 30 megakaryocytes should be evaluated Table 1. Major manifestations of dysplasia. in bone marrow. The threshold used for considering a Morphological manifestations of dysplasia. myeloid cell line as dysplastic is the presence of 10% abnormal cells in the corresponding myeloid lineage Dyserithropoiesis (Brunning et al., 2008; Hasserjian et al., 2017). Nuclear budding Identification of dysplasia is not always satisfactorily Internuclear bridging reproducible among hematopathologists (Font et al., Karyorrhesis Multinuclearity 2013; Senent et al., 2013). Several studies have been Nuclear hyperlobulation published in an attempt to improve identification of Megaloblastoid changes dysplasia of different cell types, including the following: Citoplasmic i) precise definition of myeloblasts, promyelocytes and Ring sideroblasts ring sideroblasts (Mufti et al., 2008), ii) the proposal to Vacuolitation refine the definition of dysgranulopoiesis (Goasguen et Periodic acid Shiff (PAS) positivity al., 2014), the proposal to refine the definition of dyserythropoiesis (Goasguen et al., 2018), iii) Dysgranulopoiesis identification of megakaryocytes and monocytic cells Small or unusually large size Nuclear hyposegmentation (pseudoPelger-Hüet) (Goasguen et al., 2009, 2016) and iiii) a proposal for a Nuclear hypersegmentation morphological score to detect bone marrow dysplasia Decreased granules; agranularity (Della Porta et al., 2015). The better characterization and Peudo-Chediak-Higashi granules standardization of morphological features has improved Döhle bodies the reliability and reproducibility of MDS diagnosis Auer rods (Della Porta et al., 2015; Hasserjian et al., 2017). Macropolicyte Although sometimes challenging to interpret, the Dysmegakarycytopoiesis morphologic features of MDS are well described, so that Micromegakaryocytes on the recent WHO revision for MDS, significant Nuclear hypolobulation changes related to morphologic criteria have not been Multinucleation (normal megakaryocytes are uninucleate with proposed (Hasserjian et al., 2017). For assesing lobulated nuclei) cytologic myelodysplasia it is essential to keep in mind Megakaryocytes with large peripheral cytoplasmic dilatations the morphology of normal myelopoiesis. It is also cytoplasm completely devoid of granulation with persistent basophilia 859 Cytomorphology assessment in MDS condensation with a disappearance of nucleoli and an shape. The nucleus is large, centrally placed, surrounded expulsion or enucleation of the nucleus (when the by a thin rim of deeply basophilic cytoplasm; its nucleus becomes pyknotic). Gradual changes of chromatin is a delicate and homogeneous network and cytoplasmic tonality from basophilic to acidophilic (due the nucleoli are clearly visible. The nuclear/ to haemoglobin) clearly define the passage from one cytoploplasmic ratio is very high. The cytoplasm maturation stage to the next. The different sometimes displays a lighter juxtanuclear area with a morphological categories are depicted in Fig. 1: semilunar shape that correspond to the Golgi apparatus. Proerythroblast is a large cell with a regular round (Fig. 2A-C). Basophylic erythroblast , has a reduced cell Fig. 1. General characteristics