Erythroleukaemia and RAEB-t: a same disease?

Shifting of erythroleukemia to myelodysplastic syndrome according to the revised WHO classification: Biologic and cytogenetic features of shifted erythroleukemia

The 2016 revision of the World Health Organization (WHO) classification of tumours of haematopoietic and lymphoid tissues was published. According to 2016 WHO criteria, diagnostic criteria of acute erythroid leukemia was revised. We reassessed 34 de novo acute erythroid leukemia (AEL) diagnosed by 2008 WHO criteria, according to 2016 WHO criteria. A total of 623 patients (excluding M3) with acute myeloid leukemia including 34 patients with AEL were enrolled. Among 34 patients diagnosed with AEL, diagnosis was shifted to MDS-EB in 28 patients (28/34, 82.3%) and MDS-U in 2 patients (2/34, 5.9%), while remained as AEL in 4 patients (4/34, 11.8%) according to 2016 WHO criteria. Interphase FISH for cytogenetic changes of MDS (-5/del(5q), -7/del(7q), del(20q), +8) revealed cytogenetic aberrations in 50.0% (17/34) of AEL 2008 group. AEL 2008 group showed higher frequency of complex cytogenetic abnormalities and higher MDS related cytogenetic abnormalities than AML excluding AEL group. Transformation to another AML subtype was noted in 10% in AEL shifted to MDS. Majority (88.2%) of AEL by 2008 WHO criteria was reclassified to MDS by 2016 WHO criteria. Clinical characteristics of shifted AEL were similar to those of MDS rather than de novo AML.

Changes in the World Health Organization 2016 classification of myeloid neoplasms everyone should know

PURPOSE OF REVIEW

This review highlights the main changes in the revised 2016 WHO classification of myeloid neoplasms (published in 2017) that impact diagnosis and ultimately impact management of patients with these diseases.

RECENT FINDINGS

The revision was based on data accumulated since the 2008 WHO classification, much of which relate to new molecular genetic information about these neoplasms. This massive recent influx of data concerning the significance of pathogenic mutations has affected all myeloid neoplasm categories. The new information has been incorporated as part of the diagnostic criteria of many diseases and has led to the creation of new provisional entities defined by genetic features. Germline mutations that predispose to myeloid neoplasms are also emerging as important findings that impact disease classification.

SUMMARY

The growing body of genetic data have not only altered the classification of myeloid neoplasms, but are also impacting patient management. Genetically-defined disease categories have characteristic prognoses and predicted clinical behavior. Some mutations are associated with responsiveness to certain therapies, including those that target relevant oncogenes. The disease categories in the new classification facilitate the application of risk-adapted therapy based on the most recently available data.

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.

An analysis of 97 previously diagnosed de novo adult acute erythroid leukemia patients following the 2016 revision to World Health Organization classification

Background

The incidence of acute erythroid leukemia subtype (AEL) is rare, accounting for 5% of cases of acute myeloid leukemia (AML), and the outcome is dismal. However, in 2016 revision to the WHO classification, the subcategory of AEL has been removed. Myeloblasts are redefined as the percentage of total marrow cells, not non-erythroid cells. Therefore, the previously diagnosed AEL cases are currently diagnosed as AML or myelodyspalstic syndrome (MDS) according to new criteria.

Methods

We respectively reviewed cases of 97 de novo previously diagnosed AEL and all the patients were diagnosed as AML or MDS according to the new classification scheme, and then the clinical characteristics of these two subtypes were compared. Statistical analyses were performed by SPSS software version 18.0.

Results

The median age was 37 years-old, the two-thirds of previous AEL cases were diagnosed as MDS, and there was no obvious difference between two subtypes except for male/female ratio and age. Cytogenetic, rather than MDS/AML subtypes, can better represent the prognostic factor of previously diagnosed AEL patients. When the cytogenetic risk of patients belonged to MRC intermediate category and age were below 40 years-old in previous AEL cases, the patients who received induction chemotherapy without transplantation had a similar survival compared with the patients who underwent transplantation (3-year OS: 67.2% vs 68.5%).

Conclusions

Cytogenetic, rather than MDS/AML subtypes, can better represent the prognostic factor of previously diagnosed AEL patients. Transplantation was a better choice for those whose cytogenetic category was unfavorable.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3528-6) contains supplementary material, which is available to authorized users.

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.

Erythroleukemia and Its Differential Diagnosis

Acute erythroid leukemias encompass 2 main subtypes: acute erythroleukemia (erythroid/myeloid subtype) and pure erythroid leukemia. This article reviews the main clinicopathologic features of the acute erythroid leukemias and the criteria used to diagnose them. In this article, the differential diagnosis between acute erythroid leukemias and their mimics is discussed and helpful morphologic clues and diagnostic tests that help arrive at the correct diagnosis are provided. The appropriate application of diagnostic criteria, including ancillary testing, such as immunophenotyping, cytogenetics, and molecular genetic testing, is essential to categorize bone marrow erythroid proliferations.

Erythroid proliferations in myeloid neoplasms

Prominent erythroid proliferations (in which erythroid elements comprise ≥50% of total bone marrow cells) can be seen in various hematopoietic stem cell neoplasms. The myeloproliferative neoplasm polycythemia vera exhibits effective, overexuberant erythropoiesis resulting in an increased red blood cell mass; in contrast, most other diseases characterized by erythroid predominance exhibit ineffective hemopoiesis. The latter include acute erythroid leukemia (erythroid-myeloid and pure erythroid leukemia subtypes) as well as some cases of myelodysplastic syndromes, acute myeloid leukemia with myelodysplasia-related changes, and therapy-related myeloid neoplasms. Some nonneoplastic reactive conditions may also manifest a striking bone marrow erythroid predominance. In this article, we review the literature relevant to this group of diseases for a better understanding of their clinicopathologic features and surrounding controversies. We also examine the position of neoplastic erythroid proliferations in the current 2008 World Health Organization Classification of Myeloid Neoplasms and provide recommendations as to how to approach the differential diagnosis of this group of diseases.

Comparison of genetic and clinical aspects in patients with acute myeloid leukemia and myelodysplastic syndromes all with more than 50% of bone marrow erythropoietic cells

BACKGROUND

The World Health Organization separates acute erythroid leukemia (erythropoiesis in ≥50% of nucleated bone marrow cells; ≥20% myeloblasts of non-erythroid cells) from other entities with increased erythropoiesis - acute myeloid leukemia with myelodysplasia-related changes (≥20% myeloblasts of all nucleated cells) or myelodysplastic syndromes - and subdivides acute erythroid leukemia into erythroleukemia and pure erythroid leukemia subtypes. We aimed to investigate the biological/genetic justification for the different categories of myeloid malignancies with increased erythropoiesis (≥50% of bone marrow cells).

DESIGN AND METHODS

We investigated 212 patients (aged 18.5-88.4 years) with acute myeloid leukemia or myelodysplastic syndromes characterized by 50% or more erythropoiesis: 108 had acute myeloid leukemia (77 with acute erythroid leukemia, corresponding to erythroid/myeloid erythroleukemia, 7 with pure erythroid leukemia, 24 with acute myeloid leukemia with myelodysplasia-related changes) and 104 had myelodysplastic syndromes. Morphological and chromosome banding analyses were performed in all cases; subsets of cases were analyzed by polymerase chain reaction and immunophenotyping.

RESULTS

Unfavorable karyotypes were more frequent in patients with acute myeloid leukemia than in those with myelodysplastic syndromes (42.6% versus 13.5%; P<0.0001), but their frequency did not differ significantly between patients with acute erythroid leukemia (39.0%), pure erythroid leukemia (57.1%), and acute myeloid leukemia with myelodysplasia-related changes (50.0%). The incidence of molecular mutations did not differ significantly between the different categories. The 2-year overall survival rate was better for patients with myelodysplastic syndromes than for those with acute myeloid leukemia (P<0.0001), without significant differences across the different acute leukemia subtypes. The 2-year overall survival rate was worse in patients with unfavorable karyotypes than in those with intermediate risk karyotypes (P<0.0001). In multivariate analysis, only myelodysplastic syndromes versus acute myeloid leukemia (P=0.021) and cytogenetic risk category (P=0.002) had statistically significant effects on overall survival.

CONCLUSIONS

The separation of acute myeloid leukemia and myelodysplastic syndromes with 50% or more erythropoietic cells has clinical relevance, but it might be worth discussing whether to replace the subclassifications of different subtypes of acute erythroid leukemia and acute myeloid leukemia with myelodysplasia-related changes by the single entity, acute myeloid leukemia with increased erythropoiesis ≥50%.

Erythroid-predominant myelodysplastic syndromes: enumeration of blasts from nonerythroid rather than total marrow cells provides superior risk stratification

In the FAB (French-American-British) and WHO (World Heath Organization) classifications, the blasts in erythroleukemia (M6a) are enumerated from the marrow nonerythroid rather than the total-nucleated cells. However, the method for blast calculation in erythroid-predominant myelodysplastic syndrome (erythroblasts>or=50%) is not specified either in the FAB or WHO classifications. We retrieved the files of 74 erythroid-predominant myelodysplastic syndrome patients (17% of all myelodysplastic syndrome) and 192 myelodysplastic syndrome controls (erythroblasts<50%). In erythroid-predominant myelodysplastic syndrome, by enumerating blasts from marrow nonerythroid cells rather than from total nucleated cells, 41 of 74 (55%) cases would be upgraded, either by disease subcategory or International Prognostic Scoring System. Importantly, the patients with <5% blasts demonstrated a superior survival to patients with >or=5% blasts (P=0.002); this distinction was lost when blasts were calculated from total-nucleated cells. Of cases with >or=5% blasts, cytogenetics rather than blast count correlated with survival. We conclude that in erythroid-predominant myelodysplastic syndrome, blast calculation as a proportion of marrow nonerythroid rather than total nucleated cells can better stratify patients into prognostically relevant groups.

Sub classification and clinico-hematological correlation of 40 cases of acute erythroleukemia - can proerythroblast/myeloblast and proerythroblast/total erythroid cell ratios help subclassify?

The clinico-hematological profile of 40 cases of acute erythroleukemia (AEL) was evaluated. These were subclassified into three types, namely AML M6a, M6b and M6c based on the myeloblast and proerythroblast percentages. The proerythroblast percentage has been shown to be a prognostic indicator by several studies. As AEL is biologically an "erythroid predominant" disease, two ratios (PE/MB, PE/TEC) with proerythroblasts as numerator have been formulated. An attempt has been made to assess the difference in these ratios in subclassified AEL. There were 29 M6a, 2M6b,and 9 M6 c patients, which were subclassified using the criteria proposed by Mazzella et al. The incidence of AEL in our study was 3.7%, predominantly affecting males with a predilection to younger age in contrast to Western studies. Both PE/MB and PE/TEC ratios were higher in M6b and M6c in comparison to M6a. The subclassification of AEL becomes essential especially in the era of lineage-targeted therapies, which can lead to the development and use of erythroid specific treatments in the near future.

Recommendation of the use of myeloblast percentage among non-erythroid cells instead of percentage among total nucleated cells for therapeutic response assessment in acute erythroid leukemia

The diagnostic criteria of acute erythroid leukemias (AEL) has been revised by WHO in 2001. The National Cancer Institute (NCI) published a set of standardized diagnostic and response criteria for acute myeloid leukemia in 1990, which was revised in 2003. The aim of the present study was to establish the best criteria for therapeutic response assessment in the newly classified AEL and evaluate patient outcomes. Fifty-two patients with AEL as defined by the new WHO criteria were evaluated in this study. The following seven indices for therapeutic response assessment were evaluated: (i) NCI criteria (myeloblast percentage among total nucleated cells (TNC) and cellularity); (ii) myeloblast percentage among non-erythroid cells (NEC) and cellularity; (iii) erythroid series percentage among TNC; (iv) pronormoblast percentage among erythroid cells; (v) ratio of pronormoblasts and blasts; (vi) maturation arrest index; and (vii) disappearance of erythroid dysplasia. Complete remission (CR) patients with <5% of myeloblast/NEC (NEC-CR) showed significantly longer overall survival periods (mean 55.8 months) compared to CR patients with >5% myeloblast/NEC (mean 11.7 months, P = 0.006). NEC-CR patients also had longer event-free survival (median 16.4 months) compared to patients with >5% and <20% of myeloblast/NEC (median 6.2 months) (P = 0.044). The other indices for therapeutic response assessment are not significant for predictability of relapse and outcomes. Therefore, we recommend that the myeloblast percentage among NEC be used instead of myeloblast percentage among TNC for therapeutic response assessment in AEL.