Reclassifying myelodysplastic syndromes: what's where in the new WHO and why

Erythroid nuclear dysplasia is associated with inferior outcomes for patients with myelodysplastic syndrome undergoing allogeneic hematopoietic cell transplantation

Disease burden prior to hematopoietic cell transplantation (HCT) is difficult to assess in myelodysplastic syndrome (MDS), particularly in patients without excess blasts. We assessed whether morphologic dysplasia at the time of transplant can be a metric of disease burden that is associated with post-transplant outcomes in MDS patients. We identified 84 MDS patients undergoing allogeneic HCT at our institution between 2010 and 2017 who received a bone marrow evaluation immediately prior to HCT. Dysplasia was independently determined by two hematopathologists blinded to existing pathology reports. Erythroid nuclear dysplasia, but not megakaryocytic or myeloid, was associated with post-HCT outcomes. Presence compared to absence of erythroid nuclear dysplasia was associated with lower 2-year progression-free survival (PFS; 34 % vs 62 %, p = 0.0495) and 2-year overall survival (OS; 34 % vs 62 %, p = 0.042). In a multivariate analysis including age, IPSS-R at the time of transplant, pre-HCT therapy, and donor type as covariates, erythroid nuclear dysplasia remained associated with lower PFS (HR 2.6, p = 0.036) and OS (HR 2.7, p = 0.028). Dysplasia assessment prior to transplant may serve as an estimate of disease burden in MDS and identify high-risk patients who merit additional therapies pre- or post-transplant.

Myelodysplastic syndromes and overlap syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematological neoplasms characterized by ineffective hematopoiesis, morphologic dysplasia, and cytopenia. MDS overlap syndromes include various disorders, such as myelodysplastic/myeloproliferative neoplasms and hypoplastic MDS with aplastic anemia characteristics. MDS overlap syndromes share the characteristics of other diseases, which make differential diagnoses challenging. Advances in genomic studies have led to the discovery of frequent mutations in MDS and overlap syndromes; however, most of the mutations are not specific for the diagnosis of these diseases. The molecular characteristics of the overlap syndromes usually do not show a just "in-between" form but rather heterogeneous features. Established diagnostic criteria for these diseases based on clinical, morphologic, and laboratory features are still useful when combined with genomic data. It is expected that further studies for MDS and overlap syndromes will place emphasis on the roles of mutations as therapeutic targets and prognostic indicators.

Searching Images for Consensus: Can AI Remove Observer Variability in Pathology?

One of the major obstacles in reaching diagnostic consensus is observer variability. With the recent success of artificial intelligence, particularly the deep networks, the question emerges as to whether the fundamental challenge of diagnostic imaging can now be resolved. This article briefly reviews the problem and how eventually both supervised and unsupervised AI technologies could help to overcome it.

Enumeration of CD34+ blasts by immunohistochemistry in bone marrow biopsies from MDS patients may have significant impact on final WHO classification

The percentage of blasts cells in the bone marrow (BM) of MDS patients is one of the key parameters for MDS classification and for the differential diagnosis with acute myeloid leukemia (AML). Currently, the gold standard to determine the blast percentage is conventional cytomorphology. To assess the possible impact of blast cell enumeration in BM biopsies from MDS patients on the final WHO classification using CD34 immunohistochemistry (IHC) a total of 156 BM samples from MDS and MDS-AML patients were studied and compared to blast counts by cytomorphology (CM). Eighty-nine BM aspirates were also studied by flow cytometry (FCM). Percentages of CD34+ blasts by IHC were determined blindly by two hematopathologists. Automated CD34-cell count was performed in 25 cases. Good overall agreement was found for CM and FCM with respect to critical blast thresholds (5%, 10%, 20%) (p < 0.05). However, in 17% of patients, CD34+ blast counts by IHC were higher as compared to CM with possible impact on MDS subclassification. In 7 of 21 AML patients, diagnosis was established on BM histology, while the blast percentage by CM was below the AML threshold. The assessment of CD34+ cells by IHC showed high interobserver agreement (Spearman R 0.95, p < 0.01), while automated CD34 counts were not optimal due to interference with other cellular and stromal elements. BM histology including CD34 IHC improves the diagnostic accuracy in MDS and AML. The quantification of blast cells should be based on the integration of all three methods for reliable disease classification and risk assessment.

The incidence, risk factors, and survival of acute myeloid leukemia secondary to myelodysplastic syndrome: A population-based study

To determine the incidence, risk factors, and relative survival of acute myeloid leukemia (AML) secondary to myelodysplastic syndrome (MDS) in the Surveillance, Epidemiology, and End Results (SEER) database. Retrospective analysis of all patients with new MDS onset in the SEER‐18 database from 2001 to 2013. We identified 36 558 patients with primary MDS. The rate of secondary AML (sAML) was 3.7% among patients 40 years or younger and 2.5% among those older than 40 (P = .039). The median transformation interval was significantly shorter for the younger group (4.04 vs 13.1 mo; P < .001). For both age groups, median overall and cancer‐specific survival were significantly longer for patients who did not develop sAML. Although the younger patients survived longer than the older patients, sAML development had a more negative effect on the survival of younger patients. Female sex, age, and World Health Organization (WHO) type MDS with single lineage dysplasia (MDS‐SLD) were associated with a decreased risk of sAML for older but not younger patients. Among older patients with MDS, a married status, Black race, female sex, shorter time to sAML, and WHO type MDS‐SLD or MDS with ringed sideroblasts were favorable prognostic factors for survival. In the SEER database, the rate of sAML among patients with MDS is lower than that in previous reports, but these patients still have worse survival. Risk assessment should include clinical and demographic factors.

Normal and pathological erythropoiesis in adults: from gene regulation to targeted treatment concepts

Pathological erythropoiesis with consequent anemia is a leading cause of symptomatic morbidity in internal medicine. The etiologies of anemia are complex and include reactive as well as neoplastic conditions. Clonal expansion of erythroid cells in the bone marrow may result in peripheral erythrocytosis and polycythemia but can also result in anemia when clonal cells are dysplastic and have a maturation arrest that leads to apoptosis and hinders migration, a constellation typically seen in the myelodysplastic syndromes. Rarely, clonal expansion of immature erythroid blasts results in a clinical picture resembling erythroid leukemia. Although several mechanisms underlying normal and abnormal erythropoiesis and the pathogenesis of related disorders have been deciphered in recent years, little is known about specific markers and targets through which prognosis and therapy could be improved in anemic or polycythemic patients. In order to discuss new markers, targets and novel therapeutic approaches in erythroid disorders and the related pathologies, a workshop was organized in Vienna in April 2017. The outcomes of this workshop are summarized in this review, which includes a discussion of new diagnostic and prognostic markers, the updated WHO classification, and an overview of new drugs used to stimulate or to interfere with erythropoiesis in various neoplastic and reactive conditions. The use and usefulness of established and novel erythropoiesis-stimulating agents for various indications, including myelodysplastic syndromes and other neoplasms, are also discussed.

Revisiting erythroleukemia

PURPOSE OF REVIEW

The 2016 WHO classification of hematopoietic and lymphoid neoplasms alters the diagnostic criteria for erythroleukemia, including eliminating the erythroid/myeloid type of acute erythroleukemia, which was a prior subcategory of acute myeloid leukemia, not otherwise specified. Only pure erythroid leukemia remains in the WHO classification. This review will summarize the literature that contributed to that classification change as well as recent literature on the significance of the change.

RECENT FINDINGS

There is now a large body of literature on the negative prognostic impact of erythroid predominance, defined as 50% or more bone marrow erythroid cells, in myelodysplastic syndromes (MDSs). Recent studies have found similarities between erythroleukemia, especially the erythroid/myeloid type, and the erythroid-rich MDS cases. On the basis of these data, the WHO now reclassifies cases of the prior erythroid/myeloid acute erythroleukemia group based on the total blast cell count. This change moves such cases into an MDS category, usually MDS with excess blasts. This approach, however, may cloud the significance of erythroid predominance in this group of patients.

SUMMARY

The report clarifies the current criteria for a diagnosis of erythroleukemia as well as the ongoing challenges in classifying this group of erythroid rich bone marrow disorders.

Proposed minimal diagnostic criteria for myelodysplastic syndromes (MDS) and potential pre-MDS conditions

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of myeloid neoplasms characterized by peripheral cytopenia, dysplasia, and a variable clinical course with about 30% risk to transform to secondary acute myeloid leukemia (AML). In the past 15 years, diagnostic evaluations, prognostication, and treatment of MDS have improved substantially. However, with the discovery of molecular markers and advent of novel targeted therapies, new challenges have emerged in the complex field of MDS. For example, MDS-related molecular lesions may be detectable in healthy individuals and increase in prevalence with age. Other patients exhibit persistent cytopenia of unknown etiology without dysplasia. Although these conditions are potential pre-phases of MDS they may also transform into other bone marrow neoplasms. Recently identified molecular, cytogenetic, and flow-based parameters may add in the delineation and prognostication of these conditions. However, no generally accepted integrated classification and no related criteria are as yet available. In an attempt to address this challenge, an international consensus group discussed these issues in a working conference in July 2016. The outcomes of this conference are summarized in the present article which includes criteria and a proposal for the classification of pre-MDS conditions as well as updated minimal diagnostic criteria of MDS. Moreover, we propose diagnostic standards to delineate between ´normal´, pre-MDS, and MDS. These standards and criteria should facilitate diagnostic and prognostic evaluations in clinical studies as well as in clinical practice.

Erythroleukemia shares biological features and outcome with myelodysplastic syndromes with excess blasts: a rationale for its inclusion into future classifications of myelodysplastic syndromes

Erythroleukemia was considered an acute myeloid leukemia in the 2008 World Health Organization (WHO) classification and is defined by the presence of ≥50% bone marrow erythroblasts, having <20% bone marrow blasts from total nucleated cells but ≥20% bone marrow myeloblasts from nonerythroid cells. Erythroleukemia shares clinicopathologic features with myelodysplastic syndromes, especially with erythroid-predominant myelodysplastic syndromes (≥50% bone marrow erythroblasts). The upcoming WHO revision proposes to eliminate the nonerythroid blast cell count rule and to move erythroleukemia patients into the appropriate myelodysplastic syndrome category on the basis of the absolute blast cell count. We conducted a retrospective study of patients with de novo erythroleukemia and compared their clinico-biological features and outcome with those of de novo myelodysplastic syndromes, focusing on erythroid-predominant myelodysplastic syndromes. Median overall survival of 405 erythroid-predominant myelodysplastic syndromes without excess blasts was significantly longer than that observed in 57 erythroid-predominant refractory anemias with excess blasts-1 and in 59 erythroleukemias, but no significant difference was observed between erythroid-predominant refractory anemias with excess blasts-1 and erythroleukemias. In this subset of patients with ≥50% bone marrow erythroblasts and excess blasts, the presence of a high-risk karyotype defined by the International Prognostic Scoring System or by the Revised International Prognostic Scoring System was the main prognostic factor. In the same way, the survival of 459 refractory anemias with excess blasts-2, independently of having ≥20% bone marrow blasts from nonerythroid cells or not, was almost identical to the observed in 59 erythroleukemias. Interestingly, 11 low-blast count erythroleukemias with 5 to <10% bone marrow blasts from total nucleated cells showed similar survival than the rest of erythroleukemias. Our data suggest that de novo erythroleukemia is in the spectrum of myelodysplastic syndromes with excess blasts and support its inclusion into future classifications of myelodysplastic syndromes.

Considering Bone Marrow Blasts From Nonerythroid Cellularity Improves the Prognostic Evaluation of Myelodysplastic Syndromes

PURPOSE

WHO classification of myeloid malignancies is based mainly on the percentage of bone marrow (BM) blasts. This is considered from total nucleated cells (TNCs), unless there is erythroid-hyperplasia (erythroblasts ≥ 50%), calculated from nonerythroid cells (NECs). In these instances, when BM blasts are ≥ 20%, the disorder is classified as erythroleukemia, and when BM blasts are < 20%, as myelodysplastic syndrome (MDS). In the latter, the percentage of blasts is considered from TNCs.

PATIENTS AND METHODS

We assessed the percentage of BM blasts from TNCs and NECs in 3,692 patients with MDS from the Grupo Español de Síndromes Mielodisplásicos, 465 patients with erythroid hyperplasia (MDS-E) and 3,227 patients without erythroid hyperplasia. We evaluated the relevance of both quantifications on classification and prognostication.

RESULTS

By enumerating blasts systematically from NECs, 22% of patients with MDS-E and 12% with MDS from the whole series diagnosed within WHO categories with < 5% BM blasts, were reclassified into higher-risk categories and showed a poorer overall survival than did those who remained in initial categories (P = .006 and P = .001, respectively). Following WHO recommendations, refractory anemia with excess blasts (RAEB)-2 diagnosis is not possible in MDS-E, as patients with 10% to < 20% BM blasts from TNCs fulfill erythroleukemia criteria; however, by considering blasts from NECs, 72 patients were recoded as RAEB-2 and showed an inferior overall survival than did patients with RAEB-1 without erythroid hyperplasia. Recalculating the International Prognostic Scoring System by enumerating blasts from NECs in MDS-E and in the overall MDS population reclassified approximately 9% of lower-risk patients into higher-risk categories, which indicated the survival expected for higher-risk patients.

CONCLUSION

Regardless of the presence of erythroid hyperplasia, calculating the percentage of BM blasts from NECs improves prognostic assessment of MDS. This fact should be considered in future WHO classification reviews.

Acute myeloid leukemia in the era of precision medicine: recent advances in diagnostic classification and risk stratification

Acute myeloid leukemia (AML) is a genetically heterogeneous myeloid malignancy that occurs more commonly in adults, and has an increasing incidence, most likely due to increasing age. Precise diagnostic classification of AML requires clinical and pathologic information, the latter including morphologic, immunophenotypic, cytogenetic and molecular genetic analysis. Risk stratification in AML requires cytogenetics evaluation as the most important predictor, with genetic mutations providing additional necessary information. AML with normal cytogenetics comprises about 40%-50% of all AML, and has been intensively investigated. The currently used 2008 World Health Organization classification of hematopoietic neoplasms has been proposed to be updated in 2016, also to include an update on the classification of AML, due to the continuously increasing application of genomic techniques that have led to major advances in our knowledge of the pathogenesis of AML. The purpose of this review is to describe some of these recent major advances in the diagnostic classification and risk stratification of AML.