E-cadherin is a specific marker for erythroid differentiation and has utility, in combination with CD117 and CD34, for enumerating myeloblasts in hematopoietic neoplasms

Epithelial-Mesenchymal Transition in Acute Leukemias

Epithelial-mesenchymal transition (EMT) is a metabolic process that confers phenotypic flexibility to cells and the ability to adapt to new functions. This transition is critical during embryogenesis and is required for the differentiation of many tissues and organs. EMT can also be induced in advanced-stage cancers, leading to further malignant behavior and chemotherapy resistance, resulting in an unfavorable prognosis for patients. Although EMT was long considered and studied only in solid tumors, it has been shown to be involved in the pathogenesis of hematological malignancies, including acute leukemias. Indeed, there is increasing evidence that EMT promotes the progression of acute leukemias, leading to the emergence of a more aggressive phenotype of the disease, and also causes chemotherapy resistance. The current literature suggests that the levels and activities of EMT inducers and markers can be used to predict prognosis, and that targeting EMT in addition to conventional therapies may increase treatment success in acute leukemias.

CNS erythroblastic sarcoma: a potential emerging pediatric tumor type characterized by NFIA::RUNX1T1/3 fusions

Erythroblastic sarcoma (ES) (previously called chloroma or granulocytic sarcoma) are rare hematological neoplams characterized by the proliferation of myeloid blasts at extramedullary sites, and primarily involve the skin and soft tissue of middle-aged adults. ES may be concomitant with or secondary to myeloid neoplasms (mostly acute myeloid leukemia (AML)) or in isolated cases (de novo) without infiltration of the bone marrow by blasts. ES share cytogenetic and molecular abnormalities with AML, including RUNX1T1 fusions. Some of these alterations seem to be correlated with particular sites of involvement. Herein, we report an isolated erythroblastic sarcoma with NFIA::RUNX1T1 located in the central nervous system (CNS) of a 3-year-old boy. Recently, two pediatric cases of CNS MS with complete molecular characterization have been documented. Like the current case, they concerned infants (2 and 3 years-old) presenting a brain tumor (pineal involvement) with leptomeningeal dissemination. Both cases also harbored a NFIA::RUNX1T3 fusion. ES constitutes a diagnostic challenge for neuropathologists because it does not express differentiation markers such as CD45, and may express CD99 which could be confused with CNS Ewing sarcoma. CD43 is the earliest pan-hematopoietic marker and CD45 is not expressed by erythroid lineage cells. E-cadherin (also a marker of erythroid precursors) and CD117 (expressed on the surface of erythroid lineage cells) constitute other immunhistochemical hallmarks of ES. The prognosis of patients with ES is similar to that of other patients with AML but de novo forms seem to have a poorer prognosis, like the current case. To conclude, pediatric ES with NFIA::RUNX1T1/3 fusions seem to have a tropism for the CNS and thus constitute a potential pitfall for neuropathologists. Due to the absence of circulating blasts and a DNA-methylation signature, the diagnosis must currently be made by highlighting the translocation and expression of erythroid markers.

E-cadherin/β-catenin expression is conserved in human and rat erythropoiesis and marks stress erythropoiesis

E-cadherin is a crucial regulator of epithelial cell-to-cell adhesion and an established tumor suppressor. Aside epithelia, E-cadherin expression marks the erythroid cell lineage during human but not mouse hematopoiesis. However, the role of E-cadherin in human erythropoiesis remains unknown. Because rat erythropoiesis was postulated to reflect human erythropoiesis more closely than mouse erythropoiesis, we investigated E-cadherin expression in rat erythroid progenitors. E-cadherin expression is conserved within the erythroid lineage between rat and human. In response to anemia, erythroblasts in rat bone marrow (BM) upregulate E-cadherin as well as its binding partner β-catenin. CRISPR/Cas9-mediated knock out of E-cadherin revealed that E-cadherin expression is required to stabilize β-catenin in human and rat erythroblasts. Suppression of β-catenin degradation by glycogen synthase kinase 3β (GSK3β) inhibitor CHIR99021 also enhances β-catenin stability in human erythroblasts but hampers erythroblast differentiation and survival. In contrast, direct activation of β-catenin signaling, using an inducible, stable β-catenin variant, does not perturb maturation or survival of human erythroblasts but rather enhances their differentiation. Although human erythroblasts do not respond to Wnt ligands and direct GSK3β inhibition even reduces their survival, we postulate that β-catenin stability and signaling is mostly controlled by E-cadherin in human and rat erythroblasts. In response to anemia, E-cadherin-driven upregulation and subsequent activation of β-catenin signaling may stimulate erythroblast differentiation to support stress erythropoiesis in the BM. Overall, we uncover E-cadherin/β-catenin expression to mark stress erythropoiesis in rat BM. This may provide further understanding of the underlying molecular regulation of stress erythropoiesis in the BM, which is currently poorly understood.

Digital image analysis of erythroblastic islands in myelodysplastic syndromes

INTRODUCTION

Myelodysplastic syndromes (MDS) encompass a diverse group of myeloid neoplasms for which the diagnosis of low-grade subtypes remains challenging. Erythroblastic islands (EBIs) are highly organized units of erythroid proliferation, differentiation, and enucleation. EBI disruption is frequently observed and is believed to be one of the early changes in MDS.

METHODS

In this study, we digitally analyzed bone marrow biopsies dual stained with alpha-hemoglobin stabilizing protein (AHSP) and CD163 to quantitatively study features of EBIs in MDS, among MDS subtypes, as well as those in normal marrows and marrows with other causes of anemia.

RESULTS

EBIs in MDS specimens were smaller in size and higher in density compared to both normal and non-MDS anemia specimens. Increased CD163 expression within the EBIs is observed in both MDS and other causes of anemia. A combination of increased EBI density and CD163 expression is seen in association with MDS with high-risk cytogenetics and multiple adverse mutations.

CONCLUSION

As a proof-of-concept study, we show that EBI features can be relatively easily quantified with AHSP/CD163 dual immunohistochemistry and open-source imaging analysis software, highlighting those that are unique to MDS, and which may be prognostically relevant. Further studies of the measurable EBI features may provide valuable and novel tools to aid MDS diagnosis and prognostication in the era of digital pathology.

E-Cadherin Expression Distinguishes Mouse from Human Hematopoiesis in the Basophil and Erythroid Lineages

E-cadherin is a key regulator of epithelial cell–cell adhesion, the loss of which accelerates tumor growth and invasion. E-cadherin is also expressed in hematopoietic cells as well as epithelia. The function of hematopoietic E-cadherin is, however, mostly elusive. In this study, we explored the validity of mouse models to functionally investigate the role of hematopoietic E-cadherin in human hematopoiesis. We generated a hematopoietic-specific E-cadherin knockout mouse model. In mice, hematopoietic E-cadherin is predominantly expressed within the basophil lineage, the expression of which is dispensable for the generation of basophils. However, neither E-cadherin mRNA nor protein were detected in human basophils. In contrast, human hematopoietic E-cadherin marks the erythroid lineage. E-cadherin expression in hematopoiesis thereby revealed striking evolutionary differences between the basophil and erythroid cell lineage in humans and mice. This is remarkable as E-cadherin expression in epithelia is highly conserved among vertebrates including humans and mice. Our study therefore revealed that the mouse does not represent a suitable model to study the function of E-cadherin in human hematopoiesis and an alternative means to study the role of E-cadherin in human erythropoiesis needs to be developed.

GLUT1 Immunohistochemistry Is a Highly Sensitive and Relatively Specific Marker for Erythroid Lineage in Benign and Malignant Hematopoietic Tissues

OBJECTIVES

Glucose transporter 1 (GLUT1), a glucose transporter, is an abundant protein in erythrocytes with expression beginning early in erythropoiesis. We sought to evaluate the utility of GLUT1 immunohistochemistry (IHC) as a diagnostic marker for identifying erythroid differentiation in hematopoietic tissues, including neoplastic erythroid proliferations.

METHODS

A variety of benign and neoplastic bone marrow biopsy specimens containing variable proportions of erythroid precursors were selected (n = 46, including 36 cases of leukemia). GLUT1 IHC was performed using a commercially available polyclonal antibody. Each case was evaluated for staining of erythroid precursors, nonerythroid hematopoietic cells, and blasts. A GATA1/GLUT1 double stain was performed on one case to confirm coexpression of GLUT1 on early erythroid precursors. Staining was compared with other erythroid markers, including glycophorin C.

RESULTS

GLUT1 demonstrated strong membranous staining in erythroid precursors of all cases, which was restricted largely to the erythroid lineage. Of the 36 leukemia cases, all 6 cases of pure erythroid leukemia and both cases of therapy-related acute myeloid leukemia with erythroid differentiation showed positive GLUT1 staining in blasts. Otherwise, only lymphoblasts in B-lymphoblastic leukemia showed weak to moderate granular cytoplasmic staining (four of five cases).

CONCLUSIONS

GLUT1 IHC is a highly sensitive and relatively specific marker for erythroid lineage in benign and neoplastic bone marrow biopsy specimens.

Discrete regulatory modules instruct hematopoietic lineage commitment and differentiation

Lineage commitment and differentiation is driven by the concerted action of master transcriptional regulators at their target chromatin sites. Multiple efforts have characterized the key transcription factors (TFs) that determine the various hematopoietic lineages. However, the temporal interactions between individual TFs and their chromatin targets during differentiation and how these interactions dictate lineage commitment remains poorly understood. Here we perform dense, daily, temporal profiling of chromatin accessibility (DNase I-seq) and gene expression changes (total RNA-seq) along ex vivo human erythropoiesis to comprehensively define developmentally regulated DNase I hypersensitive sites (DHSs) and transcripts. We link both distal DHSs to their target gene promoters and individual TFs to their target DHSs, revealing that the regulatory landscape is organized in distinct sequential regulatory modules that regulate lineage restriction and maturation. Finally, direct comparison of transcriptional dynamics (bulk and single-cell) and lineage potential between erythropoiesis and megakaryopoiesis uncovers differential fate commitment dynamics between the two lineages as they exit the stem and progenitor stage. Collectively, these data provide insights into the temporally regulated synergy of the cis- and the trans-regulatory components underlying hematopoietic lineage commitment and differentiation.

E-Cadherin Expression and Blunted Interferon Response in Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive neoplasm derived from plasmacytoid dendritic cells (pDCs). In this study, we investigated by immunohistochemical analysis the expression of E-cadherin (EC) on pDCs in reactive lymph nodes and tonsils, bone marrow, and in BPDCN. We compared the expression of EC in BPDCN to that in leukemia cutis (LC) and cutaneous lupus erythematosus (CLE), the latter typically featuring pDC activation. In BPDCN, we also assessed the immunomodulatory activity of malignant pDCs through the expression of several type I interferon (IFN-I) signaling effectors and downstream targets, PD-L1/CD274, and determined the extent of tumor infiltration by CD8-expressing T cells. In reactive lymph nodes and tonsils, pDCs expressed EC, whereas no reactivity was observed in bone marrow pDCs. BPDCN showed EC expression in the malignant pDCs in the vast majority of cutaneous (31/33 cases, 94%), nodal, and spleen localizations (3/3 cases, 100%), whereas it was more variable in the bone marrow (5/13, 38,5%), where tumor cells expressed EC similarly to the skin counterpart in 4 cases and differently in other 4. Notably, EC was undetectable in LC (n=30) and in juxta-epidermal pDCs in CLE (n=31). Contrary to CLE showing robust expression of IFN-I-induced proteins MX1 and ISG5 in 20/23 cases (87%), and STAT1 phosphorylation, BPDCN biopsies showed inconsistent levels of these proteins in most cases (85%). Expression of IFN-I-induced genes, IFI27, IFIT1, ISG15, RSAD2, and SIGLEC1, was also significantly (P<0.05) lower in BPDCN as compared with CLE. In BPDCN, a significantly blunted IFN-I response correlated with a poor CD8+T-cell infiltration and the lack of PD-L1/CD274 expression by the tumor cells. This study identifies EC as a novel pDC marker of diagnostic relevance in BPDCN. The results propose a scenario whereby malignant pDCs through EC-driven signaling promote the blunting of IFN-I signaling and, thereby, the establishment of a poorly immunogenic tumor microenvironment.

Combined utility of CD177, P53, CD105 and c-kit immunohistochemical stains improves the detection of myelodysplastic syndrome

The diagnosis of myelodysplastic syndrome (MDS) relies primarily on identifying peripheral blood cytopenia and morphologic dysplasia as well as detecting cytogenetic aberrations in a subset of patients. Accumulating data points to the importance of examining certain immunophenotypic changes characteristic of MDS, most of which are tested by flow cytometry. The role of immunohistochemistry in the diagnostic workup of MDS is less known. In this study, we used immunohistochemistry to survey the expression patterns of CD177, P53, CD105 and c- kit in a cohort of MDS bone marrow specimens (n = 57) and compared the results with a control group of patients who had cytopenia for other benign conditions (n = 49). MDS cases showed significant higher rates of: CD177-loss (13/57, 23% vs 1/49, 2%; P = .0016), P53 overexpression (8/57, 14% vs none; P = .005) and the presence of clusters of CD105-positive cells (6/57, 11% vs none; P = .021). Increased c-kit-positive cells was more common in MDS patients, but not statistically significant (17/57, 30% vs 8/49, 16%; P = .102). On multivariate analysis, only loss of CD177 expression was significantly higher in MDS group (P = .014). These findings suggest that a panel of immunohistochemical stains could serve as an adjunct tool in investigating unexplained cytopenias and warrant further comparative studies with flow cytometry.

Pure erythroid leukemia subsequent to acute myelomonocytic leukemia: A case report

RATIONALE

Pure erythroid leukemia is a rare subcategory of acute myeloid leukemia characterized by predominant immature erythroid population. Its occurrence subsequent to acute myelomonocytic leukemia has not been reported before. We reported this rare case to call attention because it may pose a diagnostic challenge.

PATIENTS CONCERNS

A 54-year-old female patient presented to our hospital in March 2018 with symptoms of easy fatigability.

DIAGNOSIS

Bone marrow aspiration was hypercellular showing 67.2% blasts mainly including moderate myeloblasts and monoblasts. There was mild dysplasia with some cells having round, oval, or bizarre nuclei which containing 1 to 3 nucleolus. Erythroid lineage was hypoplasia and mature erythrocytes were generally normal. Conventional cytogenetics of bone marrow cells revealed complex karyotype (44, XX, del (5) (q14q34) del (5) (q14q34), del (14) t (11;14) (q10; q10), -16, del (17), -18[10]).

INTERVENTIONS

The patient was treated with second line chemotherapy but did not respond.

QUTCOMES

She died of cardiopulmonary failure 19days after starting of therapy.

LESSONS

This unexpected and relatively uncommon occurrence was associated with a universally rapid and fatal clinical course with survival measured in <2 months despite intensive chemotherapy. We call attention to this rare phenomenon because it may pose a diagnostic challenge.

Diagnosis of rare subtypes of acute myeloid leukaemia and related neoplasms

The diagnosis of acute myeloid leukaemia and related neoplasms in adults is challenging as this requires the integration of clinical findings, morphology, immunophenotype, cytogenetics, and molecular genetic findings. Lack of familiarity with rare subtypes of acute leukaemia hinders the diagnosis. In this review, we will describe diagnostic findings of several rare acute myeloid leukaemias and related neoplasms that primarily occur in adults including information on presentation, morphology, immunophenotype, genetics, differential diagnosis, and prognosis. Leukaemias discussed include blastic plasmacytoid dendritic cell neoplasm, acute myeloid leukaemia with t(6;9) (p23;q34.1); DEK-NUP214, acute myeloid leukaemia with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOM, acute myeloid leukaemia with BCR-ABL1, acute leukaemias of ambiguous lineage, acute myeloid leukaemia with mutated RUNX1, pure erythroid leukaemia, acute panmyelosis with myelofibrosis, and acute basophilic leukaemia. Case studies with morphological features of the nine subtypes of acute myeloid leukaemia and related neoplasms have been included, and additional evidence available since publication of the 2016 World Health Organization Classification has been added to each subtype.

Clinical significance of blast percentage assessed by bone marrow trephine biopsy and aspirate smear of myeloid malignancies

The blast percentage in bone marrow (BM) can be evaluated through biopsy and aspiration, which is essential for diagnosing myeloid neoplasms especially for dividing myelodysplastic syndrome (MDS)/acute myeloid leukaemia (AML). However, methods for integrating the results of biopsy and smear have yet to be developed, particularly for cases in which the results fall on both sides of the cut-off value (10% or 20%). We studied 188 cases of MDS/AML initially diagnosed during 2011-2015 by using concomitant BM biopsy and aspiration and used different methods to compare the estimated blast percentages. A linear relationship was noted between the blast percentages estimated through biopsy and smear (R²=0.765). When the blast percentage was classified into four relevant clinical categories (<5%, 5-9%, 10-19%, and ≥20%), the total concordance between the results of the biopsy and smear was 76.1%. Although the prognostic values obtained through biopsy and smear were not significantly different, using the higher blast percentage estimation by biopsy and smear fared better in classifying patients into categories of 10-19% and ≥20% and demonstrated survival significance in both univariate and multivariate analyses. Subgroup analyses demonstrated that BM blast percentages had no prognostic significance when patients underwent intensive chemotherapy. However, blast percentages of ≥10% indicated poor prognosis for patients receiving only supportive care. In conclusion, most of the clinically relevant categories of blast percentages estimated through concomitant BM biopsy and smear were concordant. When the categories were different, the best prognostic prediction method was to select the higher blast percentage determined through biopsy and smear to diagnose MDS/AML.

Flow Cytometry Analysis Versus E-Cadherin Immunohistochemistry for the Diagnosis of Pure Erythroid Leukemia: A Case Report

Pure erythroid leukemia (PEL) is a rare form of acute myeloid leukemia characterized by the neoplastic proliferation of erythroblasts. PEL is associated with inferior survival outcomes, particularly among patients harboring complex karyotype abnormalities. In this case, we present a 21-year-old Sudanese man who presented to our ER with a two-week history of fever, shortness of breath, fatigue, and exercise intolerance. He had no significant personal medical history or family history of malignancy. A bone marrow biopsy revealed hypercellularity and infiltration by cells with an immature appearance. A flow cytometry (FC) analysis of the bone marrow aspirate revealed that approximately 21% of the total nucleated cells were negative for CD45 and positive for CD71, glycophorin A, and CD36 but negative for myeloperoxidase (MPO), CD33, CD13, CD61, CD41, and other lymphoid and myeloid markers. Consistent with the microscopic analysis, <1% of the total cells were identified as CD34/CD13/CD117-positive myeloblasts. Notably, all stains (CD45, MPO, CD34, CD163, CD61, glycophorin A) were negative except E-cadherin, which positively stained >80% of the cells. Our findings suggested a differential diagnosis that included erythroid leukemia and myelodysplastic syndrome (MDS). The morphological, FC, immunohistochemistry, and cytogenetic findings strongly supported a diagnosis of PEL.

E-Cadherin Expression in Blastic Plasmacytoid Dendritic Cell Neoplasms: An Unrecognized Finding and Potential Diagnostic Pitfall

E-cadherin is expressed in hematopoietic erythroid precursors, but to our knowledge, its expression in blastic plasmacytoid dendritic cell neoplasm (BPDCN) has not been described. We report a case of BPDCN showing strong expression of E-cadherin, arising in a patient with history of primary myelofibrosis. Four more cases of BPDCN tested all showed strong expression of E-cadherin. Lack of awareness of this pattern of expression may lead to erroneous diagnosis of acute erythroid leukemia. It is increasingly becoming important to correctly identify this group of neoplasms, as approved new anti-CD123-targeted therapies are becoming available.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

Myelodysplastic/myeloproliferative neoplasms: are morphology and immunophenotyping still relevant?

The term myelodysplastic/myeloproliferative neoplasm (MDS/MPN) refers to a group of clonal hematopoietic neoplasms with overlapping clinical, morphologic and genetic myelodysplastic and myeloproliferative features observed at the time of first presentation. Impaired hematopoiesis morphologically associated with evidence of myelodysplasia manifests clinically with cytopenia/s. Simultaneously, myeloproliferation is seen within the bone marrow and leads to cytosis in the peripheral blood. The diagnostic category of MDS/MPN encompasses a heterogeneous group of diseases which share similarities among them, but at the same time have distinct clinical and pathologic features and eventually diverse prognosis; such differences justify their separation in a classification scheme. In the era of genetic and genomic tests, their distinction from conventional myelodysplastic syndromes or myeloproliferative neoplasms still relies on close clinocopathological correlation, with evaluation of both peripheral blood and bone marrow samples being essential in this sense. A multiparametric integration of clinicopathologic data and cytogenetics and molecular genetics results is the preferred diagnostic approach.

Oncogenic Deregulation of Cell Adhesion Molecules in Leukemia

Numerous cell⁻cell and cell⁻matrix interactions within the bone marrow microenvironment enable the controlled lifelong self-renewal and progeny of hematopoietic stem and progenitor cells (HSPCs). On the cellular level, this highly mutual interaction is granted by cell adhesion molecules (CAMs) integrating differentiation, proliferation, and pro-survival signals from the surrounding microenvironment to the inner cell. However, cell⁻cell and cell⁻matrix interactions are also critically involved during malignant transformation of hematopoietic stem/progenitor cells. It has become increasingly apparent that leukemia-associated gene products, such as activated tyrosine kinases and fusion proteins resulting from chromosomal translocations, directly regulate the activation status of adhesion molecules, thereby directing the leukemic phenotype. These observations imply that interference with adhesion molecule function represents a promising treatment strategy to target pre-leukemic and leukemic lesions within the bone marrow niche. Focusing on myeloid leukemia, we provide a current overview of the mechanisms by which leukemogenic gene products hijack control of cellular adhesion to subsequently disturb normal hematopoiesis and promote leukemia development.

Cell-adhesion molecules and their soluble forms: Promising predictors of "tumor progression" and relapse in leukemia

Some surface markers are used to discriminate certain leukemic subpopulations that retain a greater oncogenic potential than others, and, for this reason, they were termed as leukemic stem cells, similar to the concept of cancer stem cells in carcinoma. Among these surface markers are proteins involved in cell-cell adhesion or cell-matrix adhesion, and they may play a role in the relapse of leukemia, similar to metastasis in carcinomas. The most important are epithelial cadherin, neural cadherin, epithelial cell-adhesion molecule, and CD44, which can be cleaved and released, and their soluble forms were found increased in serum levels of cancer patients, being implicated, in some cases, with progression, metastases, and relapse. In this review, we highlighted the role of these four adhesion molecules in carcinomas and hematological malignancies, mainly leukemia, and discuss if the serum levels of soluble forms can be correlated with the surface protein status on the leukemic cells. Accession of the soluble forms looks attractive, but their use as markers in cancer must be studied in association with other parameters, as there are significant changes in levels in other pathological conditions besides cancer. Studies correlating the levels of the forms with the status of the membrane-bound proteins in leukemic (stem) cells and correlating those parameters with relapse in leukemia may afford important knowledge and applicability of those serum markers in clinical practice. For instance, the expression of the membrane-bound forms of these adhesion proteins may have promising clinical use in leukemia and other hematological malignancies.

Disruption of the BCL11A Erythroid Enhancer Reactivates Fetal Hemoglobin in Erythroid Cells of Patients with β-Thalassemia Major

In the present report, we carried out clinical-scale editing in adult mobilized CD34+ hematopoietic stem and progenitor cells (HSPCs) using zinc-finger nuclease-mediated disruption of BCL11a to upregulate the expression of γ-globin (fetal hemoglobin). In these cells, disruption of the erythroid-specific enhancer of the BCL11A gene increased endogenous γ-globin expression to levels that reached or exceeded those observed following knockout of the BCL11A coding region without negatively affecting survival or in vivo long-term proliferation of edited HSPCs and other lineages. In addition, BCL11A enhancer modification in mobilized CD34+ cells from patients with β-thalassemia major resulted in a readily detectable γ-globin increase with a preferential increase in G-gamma, leading to an improved phenotype and, likely, a survival advantage for maturing erythroid cells after editing. Furthermore, we documented that both normal and β-thalassemia HSPCs not only can be efficiently expanded ex vivo after editing but can also be successfully edited post-expansion, resulting in enhanced early in vivo engraftment compared with unexpanded cells. Overall, this work highlights a novel and effective treatment strategy for correcting the β-thalassemia phenotype by genome editing.

HBME-1 is expressed by erythroid precursors in early maturation stage and can be a valuable tool for evaluation of dyserythropoiesis in bone marrow core biopsy specimens

The reaction of Hector Battifora mesothelial epitope-1 (HBME-1) antibody with scattered pronormoblasts in normal bone marrow core biopsy specimens has been reported. This study evaluated the immunohistochemical profile of HBME-1 in a panel of 52 normal, dyserythropoietic and neoplastic marrow samples. We compared the staining property of HBME-1 with that of the commonly used erythroid marker, glycophorin A (CD235a) and in each case, we semi-quantitatively evaluated the HBME-1/CD235a-positive cells ratio. In normal samples, HBME-1 labelled scattered immature erythroid precursors. In dyserythropoietic specimens, HBME-1 stained nucleated erythroid precursors in varying degrees, from pronormoblast through normoblast stages, with the highest intensity in immature forms. Overall, the cellular background of non-erythroid progenitors, erythrocytes and neoplastic cells did not react with HBME-1, except in leukaemia cases with myelodysplasia-related changes. Our study shows that HBME-1 is a useful marker to identify immature erythroid precursors and that an HBME-1/CD235a-positive cells ratio ≥10% is associated with dyserythropoiesis.

Do Not Forget the Glycophorin A: An Unusual Case of Myeloid Sarcoma

Acute erythroid leukemia is rare, with isolated reports on presentation as an extramedullary tumor mass (myeloid sarcoma). We describe a case of pure erythroid leukemia presenting as an orbital mass in a 1-year, 9-month-old girl. This is only the second case described in a child. Tissue biopsy of the tumor mass showed medium-sized cells that were glycophorin A positive and negative with conventional myeloid markers. Flow cytometry, bone marrow aspirate, and trephine confirmed the diagnosis of pure erythroid leukemia.

Acute Erythroleukemias, Acute Megakaryoblastic Leukemias, and Reactive Mimics: A Guide to a Number of Perplexing Entities

OBJECTIVES

At the 2013 Society for Hematopathology/European Association for Hematopathology Workshop, 36 cases were submitted to the session that covered acute erythroid leukemia (AEL), acute megakaryoblastic leukemia (AMKL), and reactive mimics.

METHODS

Cases were reviewed by the session chairs and workshop panel to reach a consensus diagnosis.

RESULTS

For acute erythroleukemia, erythroid/myeloid type, discussion acknowledged overlapping features between AEL and myelodysplastic syndromes. Cases submitted as pure erythroid leukemia had distinctive morphology and immunophenotype, complex karyotypes, and aggressive clinical behavior, illustrating certain diagnostic features not currently captured by the current World Health Organization (WHO) definition. In Down syndrome, there were striking similarities between transient abnormal myelopoiesis and AMKL. Most cases of AMKL in adults would be classified as acute myeloid leukemia with myelodysplasia-related changes according to the WHO classification, but this approach deemphasizes their unique clinical, morphologic, and immunophenotypic features.

CONCLUSIONS

The broad spectrum of cases illustrated the difficulties and complex issues involved in establishing a diagnosis of these entities and the need for better disease definitions.

How unique is pure erythroid leukaemia? A retrospective analysis of seven cases and review of the literature

AIMS

Pure erythroid leukaemia (PEL) is a rare subtype of acute myeloid leukaemia (AML) and its clinicopathological features are not well-defined. The aim of this study was to describe the immunophenotypic, cytogenetic and clinical features of PEL and to compare these with cases of AML with ≥ 50% erythroblasts.

METHODS

Cases of PEL according to WHO morphological criteria diagnosed at three institutions from 1997 to 2013 were included. A comparison cohort comprised of AML with ≥ 50% erythroblasts. The clinical, histopathology, immunophenotypic and cytogenetic features of cases were analysed. We also reviewed the existing literature on PEL, and combined our cohort with previously reported cases of PEL in a pooled analysis.

RESULTS

There were seven cases of PEL diagnosed at our institutions. There was a high incidence of either prior chemoradiotherapy exposure or evolution from pre-existing myelodysplastic syndrome (MDS) (71%). The leukaemic blasts frequently expressed glycophorin C (100%), CD117 (83%) and were myeloperoxidase negative (83%). Complex karyotypes were present in 83% of cases. Median overall survival was 2.9 months. Compared with AML with ≥ 50% erythroblasts, cases of PEL demonstrated a higher incidence of adverse-risk cytogenetics (p=0.01) and prior exposure to chemoradiotherapy (p=0.01).

CONCLUSIONS

PEL appears to be a unique entity that is often secondary or therapy related, commonly features a complex karyotype and has a poor prognosis. It is morphologically and immunophenotypically distinct from other cases of AML with erythroid hyperplasia.