The World Health Organization (WHO) classification of the myeloid neoplasms

A World Health Organization (WHO) classification of hematopoietic and lymphoid neoplasms has recently been published. This classification was developed through the collaborative efforts of the Society for Hematopathology, the European Association of Hematopathologists, and more than 100 clinical hematologists and scientists who are internationally recognized for their expertise in hematopoietic neoplasms. For the lymphoid neoplasms, this classification provides a refinement of the entities described in the Revised European-American Lymphoma (REAL) Classification-a system that is now used worldwide. To date, however, there has been no published explanation or rationale given for the WHO classification of the myeloid neoplasms. The purpose of this communication is to outline briefly the WHO classification of malignant myeloid diseases, to draw attention to major differences between it and antecedent classification schemes, and to provide the rationale for those differences.

International Classification of Childhood Cancer, third edition

BACKGROUND

The third edition of the International Classification of Diseases for Oncology (ICD-O-3), which was published in 2000, introduced major changes in coding and classification of neoplasms, notably for leukemias and lymphomas, which are important groups of cancer types that occur in childhood. This necessitated a third revision of the 1996 International Classification of Childhood Cancer (ICCC-3).

METHODS

The tumor categories for the ICCC-3 were designed to respect several principles: agreement with current international standards, integration of the entities defined by newly developed diagnostic techniques, continuity with previous childhood classifications, and exhaustiveness.

RESULTS

The ICCC-3 classifies tumors coded according to the ICD-O-3 into 12 main groups, which are split further into 47 subgroups. These 2 levels of the ICCC-3 allow standardized comparisons of the broad categories of childhood neoplasms in continuity with the previous classifications. The 16 most heterogeneous subgroups are broken down further into 2-11 divisions to allow study of important entities or homogeneous collections of tumors characterized at the cytogenetic or molecular level. Some divisions may be combined across the higher-level categories, such as the B-cell neoplasms within leukemias and lymphomas.

CONCLUSIONS

The ICCC-3 respects currently existing international standards and was designed for use in international, population-based, epidemiological studies and cancer registries. The use of an international classification system is especially important in the field of pediatric oncology, in which the low frequency of cases requires rigorous procedures to ensure data comparability.

Prognostic Factors and Life Expectancy in Myelodysplastic Syndromes Classified According to WHO Criteria: A Basis for Clinical Decision Making

Purpose

The aim of this study was to evaluate the prognostic value of the WHO proposal, to assess the role of the main prognostic factors in myelodysplastic syndromes (MDSs) classified into WHO subgroups, and to estimate mortality (standardized mortality ratio [SMR]) and life expectancy in these groups as a basis for clinical decision making.

Patients and Methods

Four hundred sixty-seven patients who were diagnosed as having de novo MDS at the Division of Hematology, University of Pavia (Pavia, Italy), between 1992 and 2002, were evaluated retrospectively for clinical and hematologic features at diagnosis, overall survival (OS), and progression to leukemia (leukemia-free survival).

Results

Significant differences in survival were noted between patients with refractory anemia (RA), refractory cytopenia with multilineage dysplasia, RA with excess blasts, type 1 (RAEB-1), and RAEB-2. The effect of demographic factors on OS was observed in MDS patients without excess blasts (age, P = .001; sex, P = .006), as in the general population. The mortality of RA patients 70 years or older did not differ significantly from that of the general population (SMR, 1.62; P = .06). Cytogenetics was the only International Prognostic Scoring System variable showing a prognostic value in MDS classified into WHO subgroups. Transfusion-dependent patients had a significantly shorter survival than patients who did not require transfusions (P < .001). Developing a secondary iron overload significantly affected the survival of transfusion-dependent patients (P = .003).

Conclusion

These data show that the WHO classification of MDSs has a relevant prognostic value. This classification, along with cytogenetics, might be useful in decisions regarding transplantation. MDS with isolated erythroid lineage dysplasia identifies a subset of truly low-risk patients, for whom a conservative approach is advisable.

New insights into the prognostic impact of the karyotype in MDS and correlation with subtypes: evidence from a core dataset of 2124 patients

We have generated a large, unique database that includes morphologic, clinical, cytogenetic, and follow-up data from 2124 patients with myelodysplastic syndromes (MDSs) at 4 institutions in Austria and 4 in Germany. Cytogenetic analyses were successfully performed in 2072 (97.6%) patients, revealing clonal abnormalities in 1084 (52.3%) patients. Numeric and structural chromosomal abnormalities were documented for each patient and subdivided further according to the number of additional abnormalities. Thus, 684 different cytogenetic categories were identified. The impact of the karyotype on the natural course of the disease was studied in 1286 patients treated with supportive care only. Median survival was 53.4 months for patients with normal karyotypes (n = 612) and 8.7 months for those with complex anomalies (n = 166). A total of 13 rare abnormalities were identified with good (+1/+1q, t(1q), t(7q), del(9q), del(12p), chromosome 15 anomalies, t(17q), monosomy 21, trisomy 21, and -X), intermediate (del(11q), chromosome 19 anomalies), or poor (t(5q)) prognostic impact, respectively. The prognostic relevance of additional abnormalities varied considerably depending on the chromosomes affected. For all World Health Organization (WHO) and French-American-British (FAB) classification system subtypes, the karyotype provided additional prognostic information. Our analyses offer new insights into the prognostic significance of rare chromosomal abnormalities and specific karyotypic combinations in MDS.

Definitions and standards in the diagnosis and treatment of the myelodysplastic syndromes: Consensus statements and report from a working conference

The classification, scoring systems, and response criteria for myelodysplastic syndromes (MDS) have recently been updated and have become widely accepted. In addition, several new effective targeted drugs for patients with MDS have been developed. The current article provides a summary of updated and newly proposed markers, criteria, and standards in MDS, with special reference to the diagnostic interface and refinements in evaluations and scoring. Concerning the diagnostic interface, minimal diagnostic criteria for MDS are proposed, and for patients with unexplained cytopenia who do not fulfill these criteria, the term 'idiopathic cytopenia of uncertain significance' (ICUS) is suggested. In addition, new diagnostic and prognostic parameters, histopathologic and immunologic determinants, proposed refinements in scoring systems, and new therapeutic approaches are discussed. Respective algorithms and recommendations should facilitate diagnostic and prognostic evaluations in MDS, selection of patients for therapies, and the conduct of clinical trials.

A pediatric approach to the WHO classification of myelodysplastic and myeloproliferative diseases

Myelodysplastic and myeloproliferative disorders are rare in childhood and there is no widely accepted system for their diagnosis and classification. We propose minimal diagnostic criteria and a simple classification scheme which, while based on accepted morphological features and conforming with the recent suggestions of the WHO, allows for the special problems of myelodysplastic diseases in children. The classification recognizes three major diagnostic groups: (1) juvenile myelomonocytic leukemia (JMML), previously named chronic myelomonocytic leukemia (CMML) or juvenile chronic myeloid leukemia (JCML); (2) myeloid leukemia of Down syndrome, a disease with distinct clinical and biological features, encompassing both MDS and AML occurring in Down syndrome; and (3) MDS occurring both de novo and as a complication of previous therapy or pre-existing bone marrow disorder (secondary MDS). The main subtypes of MDS are refractory cytopenia (RC) and refractory anemia with excess of blasts (RAEB). It is suggested retaining the subtype of RAEB-T with 20-30% blasts in the marrow until more data are available. Cytogenetics and serial assessments of the patients are essential adjuncts to morphology both in diagnosis and classification.

SF3B1-mutant MDS as a distinct disease subtype: a proposal from the International Working Group for the Prognosis of MDS

The 2016 revision of the World Health Organization classification of tumors of hematopoietic and lymphoid tissues is characterized by a closer integration of morphology and molecular genetics. Notwithstanding, the myelodysplastic syndrome (MDS) with isolated del(5q) remains so far the only MDS subtype defined by a genetic abnormality. Approximately half of MDS patients carry somatic mutations in spliceosome genes, with SF3B1 being the most commonly mutated one. SF3B1 mutation identifies a condition characterized by ring sideroblasts (RS), ineffective erythropoiesis, and indolent clinical course. A large body of evidence supports recognition of SF3B1-mutant MDS as a distinct nosologic entity. To further validate this notion, we interrogated the data set of the International Working Group for the Prognosis of MDS (IWG-PM). Based on the findings of our analyses, we propose the following diagnostic criteria for SF3B1-mutant MDS: (1) cytopenia as defined by standard hematologic values, (2) somatic SF3B1 mutation, (3) morphologic dysplasia (with or without RS), and (4) bone marrow blasts <5% and peripheral blood blasts <1%. Selected concomitant genetic lesions represent exclusion criteria for the proposed entity. In patients with clonal cytopenia of undetermined significance, SF3B1 mutation is almost invariably associated with subsequent development of overt MDS with RS, suggesting that this genetic lesion might provide presumptive evidence of MDS in the setting of persistent unexplained cytopenia. Diagnosis of SF3B1-mutant MDS has considerable clinical implications in terms of risk stratification and therapeutic decision making. In fact, this condition has a relatively good prognosis and may respond to luspatercept with abolishment of the transfusion requirement.

Driver somatic mutations identify distinct disease entities within myeloid neoplasms with myelodysplasia

Our knowledge of the genetic basis of myelodysplastic syndromes (MDS) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) has considerably improved. To define genotype/phenotype relationships of clinical relevance, we studied 308 patients with MDS, MDS/MPN, or acute myeloid leukemia evolving from MDS. Unsupervised statistical analysis, including the World Health Organization classification criteria and somatic mutations, showed that MDS associated with SF3B1-mutation (51 of 245 patients, 20.8%) is a distinct nosologic entity irrespective of current morphologic classification criteria. Conversely, MDS with ring sideroblasts with nonmutated SF3B1 segregated in different clusters with other MDS subtypes. Mutations of genes involved in DNA methylation, splicing factors other than SF3B1, and genes of the RAS pathway and cohesin complex were independently associated with multilineage dysplasia and identified a distinct subset (51 of 245 patients, 20.8%). No recurrent mutation pattern correlated with unilineage dysplasia without ring sideroblasts. Irrespective of driver somatic mutations, a threshold of 5% bone marrow blasts retained a significant discriminant value for identifying cases with clonal evolution. Comutation of TET2 and SRSF2 was highly predictive of a myeloid neoplasm characterized by myelodysplasia and monocytosis, including but not limited to, chronic myelomonocytic leukemia. These results serve as a proof of concept that a molecular classification of myeloid neoplasms is feasible.

Validation of the WHO proposals for a new classification of primary myelodysplastic syndromes: a retrospective analysis of 1600 patients

In 1982, the French-American-British (FAB) cooperative group proposed a classification of myelodysplastic syndromes (MDS) based on morphological features in blood and bone marrow, namely on medullary and peripheral blast count, Auer rods, ring sideroblasts and the number of monocytes in the peripheral blood. This classification has been used for numerous studies regarding morphology, prognosis and treatment of MDS. Some details of this morphological classification remained unclear, and some patients were unclassifiable. A working group of the World Health Organization (WHO) recently proposed a new classification of MDS, based on a significant modification of the original FAB proposals. CMML and RAEB-T were removed from the MDS classification and RAEB was split into two groups with medullary blast counts below and above 10%. In addition, a group of patients with less than 5% medullary blasts but evidence of multilineage dysplasia was defined. MDS patients with 5q- as the sole chromosomal anomaly were also considered a separate group. The aim of the present study was to validate the new classification with respect to prognostic importance, and to correlate it with cytogenetic and hematological features in a large series of patients (n=1600) with a long-term follow up. We were able to confirm a significant difference in prognosis between RAEB I and RAEB II, as well as a difference between refractory anemia and multilineage dysplasia. Furthermore, patients with 5q- anomaly had a much better prognosis than other WHO subtypes, but this was only true for patients with a medullary blast count below 5%. In summary, the WHO classification appears to define morphological subgroups that are more homogeneous with respect to prognosis than the FAB subtypes.

TP53 mutation status divides myelodysplastic syndromes with complex karyotypes into distinct prognostic subgroups

Risk stratification is critical in the care of patients with myelodysplastic syndromes (MDS). Approximately 10% have a complex karyotype (CK), defined as more than two cytogenetic abnormalities, which is a highly adverse prognostic marker. However, CK-MDS can carry a wide range of chromosomal abnormalities and somatic mutations. To refine risk stratification of CK-MDS patients, we examined data from 359 CK-MDS patients shared by the International Working Group for MDS. Mutations were underrepresented with the exception of TP53 mutations, identified in 55% of patients. TP53 mutated patients had even fewer co-mutated genes but were enriched for the del(5q) chromosomal abnormality (p < 0.005), monosomal karyotype (p < 0.001), and high complexity, defined as more than 4 cytogenetic abnormalities (p < 0.001). Monosomal karyotype, high complexity, and TP53 mutation were individually associated with shorter overall survival, but monosomal status was not significant in a multivariable model. Multivariable survival modeling identified severe anemia (hemoglobin < 8.0 g/dL), NRAS mutation, SF3B1 mutation, TP53 mutation, elevated blast percentage (>10%), abnormal 3q, abnormal 9, and monosomy 7 as having the greatest survival risk. The poor risk associated with CK-MDS is driven by its association with prognostically adverse TP53 mutations and can be refined by considering clinical and karyotype features.

Refined chromosome study helps define prognostic subgroups in most patients with primary myelodysplastic syndrome and acute myelogenous leukaemia

Based on a 6 1/2-year study of 284 consecutive adult patients with primary myelodysplastic syndrome (MDS) and and acute myelogenous leukaemia (AML), we have found that refined chromosome analysis can be used as an independent prognostic indicator in the great majority of patients with MDS and AML. In MDS, the FAB subtype was also found to have prognostic value and this was enhanced when the chromosomal findings were taken into consideration. In AML, the age of the patient correlated more closely with the chromosomal changes in predicting prognosis in most patients than did the FAB classification. Previously we reported that refined chromosome analysis of bone marrow specimens from 161 adult patients with primary or non-therapy related MDS and AML identified three prognostic chromosomal categories in each disease, representing 40% of all patients (Yunis et al, 1984, 1986). By extending our study to 284 patients, as well as a longer follow-up, it was possible to determine the prognostic implications of two additional chromosomal categories in MDS and five in AML. Since 73% of all patients are now represented in well-defined chromosomal subgroups with prognostic significance, refined chromosome analysis emerges as a tool that could have considerable impact in protocols.

Cytogenetic features in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) comprise a group of bone marrow diseases characterized by profound heterogeneity in morphologic presentation, clinical course, and cytogenetic features. Roughly 50% of patients display clonal chromosome abnormalities. In several multicentric studies, the karyotype turned out to be one of the most important prognostic parameters and was incorporated into statistical models aiming for a better prediction of the individual prognosis like the International Prognostic Scoring System. However, due to the profound cytogenetic heterogeneity, the impact of many rare abnormalities as well as combinations of anomalies occurring in a substantial portion of patients with MDS is still unknown and can only be delineated on the basis of large international multicentric cooperations. Recently, the German-Austrian MDS Study Group presented cytogenetic findings in 2,072 patients with MDS, which serve as a basis for the characterization of the cytogenetic subgroups discussed in this article. The availability of new therapeutic options for low- and high-risk MDS targeted against distinct entities characterized by specific chromosome abnormalities, like 5q-deletions, monosomy 7, and complex abnormalities underlines the important role of cytogenetics for the clinical management of MDS. This article thus focuses on the clinical and prognostic relevance, the molecular background, and therapeutic perspectives in these three cytogenetic subgroups.

Utility of the FAB classification for myelodysplastic syndromes: investigation of prognostic factors in 237 cases

The utility and prognostic significance of the FAB classification was studied in 237 patients with a myelodysplastic syndrome. No significant differences in actuarial survival and probability of transformation to acute leukaemia were found in patients with RA, AISA or CMML. The median survival time for the RA group was 50 months, for the AISA and CMML subclasses more than 60 months. The probability of transformation for the RA, AISA and CMML subgroups showed a linear trend with a probability of 25% for the RA, 16% for the AISA and of 18% for the CMML groups after a 5 year observation period. A uniformly poor prognosis was found for the RAEB and RAEB/t subgroups with median survival times of respectively 9 and 6 months. Chromosomal abnormalities were found in 68 out of 155 patients (44%). Patients with only normal metaphases or with abnormal metaphases together with karyotypic normal cells had a longer median survival time and a lower probability for transformation as compared to those with only abnormal metaphases. The most important factor in prognosis is the number of blast cells in blood and bone marrow. Age and sex, and certain quantitative and qualitative abnormalities in the peripheral blood appear of limited prognostic value for patients with RA, AISA and CMML. The longer life expectancy of 35 patients with CMML as compared to other series seems to be related to the percentage of blast cells at the time of diagnosis.

Age-related incidence and other epidemiological aspects of myelodysplastic syndromes

Although most haematologists perceive a rising prevalence and incidence of myelodysplastic syndromes (MDS), reliable epidemiological data on these disorders are largely lacking. The bone marrow register of the University of Düsseldorf allowed us to assess among other epidemiological features the incidence of MDS, which was compared to that of acute myeloid leukaemia (AML). Among a total of 18,416 different patients registered between 1975 and 1990, 584 cases of MDS (3.2%) and 506 cases of AML (2.8%) were identified. Over the study period, the percentage of newly diagnosed MDS rose from 1.3% to 4.5%, while there was no upward trend for AML. Among all patients undergoing bone marrow biopsy, the proportion of those over 60 years of age increased from 41.9% in 1975 to 54.1% in 1990. We found a strong correlation between the proportion of elderly patients and the relative frequency of MDS diagnoses. Thirty-one patients (5.3%) were classified as a secondary MDS because of previous treatment with cytotoxic chemotherapy and/or irradiation for a variety of malignancies. Twelve patients were identified in whom occupational exposure to organic solvents could not be ruled out. For calculating age-specific incidence rates, the analysis was confined to the town district of Düsseldorf (575,000 inhabitants), because exact demographical data were available for this population. In the last quinquennium of the study period (1986-90), myelodysplastic syndromes were more frequent than AML in the age group 50-70 years (4.9 v 1.8/100,000/year). In patients over 70, the incidence of MDS was more than 3 times that of AML (22.8 v 6.7/100,000). In this group, men had a higher incidence of MDS (33.9/100,000) than women (18/100,000). Crude annual incidence (all age groups) was also higher for MDS (4.1/100,000) than for AML (2.1/100,000) in recent years. We conclude that MDS are relatively common haematological neoplasias. The rising incidence in recent years is probably not due to changes in aetiological factors, but may reflect increased awareness on the part of physicians and extended use of diagnostic procedures in elderly patients.

Histopathology in the diagnosis and classification of acute myeloid leukemia, myelodysplastic syndromes, and myelodysplastic/myeloproliferative diseases

In spite of the impressive advances in the area of molecular pathology, bone marrow morphology remains the diagnosis cornerstone to identify the various subtypes of myeloid neoplasms. Morphological examination of the bone marrow requires both bone marrow aspirate and bone marrow trephine biopsy. Immunohistochemistry of bone marrow biopsy with markers reactive in paraffin-embedded tissues represents a powerful diagnostic tool; its results can be easily correlated with those obtained by other techniques such as flow cytometry and genetic analysis, and above all, the clinical findings. The role of the bone marrow biopsy will be particularly stressed in this review article. Particular emphasis is being given to the correct identification of cases of myeloid neoplasms associated with myelofibrosis and for which the bone marrow biopsy represents the only available diagnostic mean. Moreover, the often low cellular yield of the bone marrow aspirate in these cases may also be insufficient to obtain adequate cytogenetic information. Such cases include two subtypes of acute myeloid leukemia which typically cause diagnostic difficulties: acute megakaryoblastic leukemia and acute panmyelosis with myelofibrosis (acute myelosclerosis). Acute myeloid leukemia with multilineage dysplasia, therapy-related myelodysplastic syndrome/therapy-related acute myeloid leukemia and de novo myelodysplastic syndromes (MDS) will also be discussed. The value of bone marrow biopsy in this group of disorders is generally well established. In MDS, in particular, bone marrow biopsy may help in confirming a suspected diagnosis by excluding reactive conditions in which dyshematopoietic changes may also be observed. It can increase the diagnostic accuracy and helps in refining the IPPS risk evaluation system. Among the alterations detected by bone marrow biopsy, a prognostically important finding is the presence of aggregates or clusters of immature myeloid precursor cells (myeloblasts and promyelocytes). These can also be identified by immunohistochemistry with CD34, an antigen expressed in progenitor and early precursor marrow cells, which can be used to demonstrate pathological accumulations of blasts in aggressive subtypes of myeloid neoplasms. Immunohistologic analysis is especially helpful in cases of MDS with fibrosis and cases with hypocellular marrows (hypoplastic MDS). In both of these variants, the presence of reticulin fibrosis or fatty changes in the bone marrow can make accurate disease characterization very difficult or impossible using bone marrow aspirates. Finally, the important group of the myelodysplastic/myeloproliferative disorders can only be accurately categorized by a careful multiparametric approach in which the bone marrow biopsy exerts a pivotal role.

Refinement of the international prognostic scoring system (IPSS) by including LDH as an additional prognostic variable to improve risk assessment in patients with primary myelodysplastic syndromes (MDS)

The international prognostic scoring system (IPSS) is considered the gold standard for risk assessment in primary myelodysplastic syndromes (MDS). This score includes several prognostic factors except serum lactate dehydrogenase (LDH). We evaluated the prognostic power of LDH as an additional variable in IPSS-based risk assessment. For this purpose, a total of 892 patients with primary MDS registered by the Austrian-German cooperative MDS study group was analyzed retrospectively. Multivariate analysis confirmed the value of established parameters such as medullary blasts, karyotype and peripheral cell counts and showed that elevated LDH was associated with decreased overall survival (P<0.00005) and increased risk of AML development (P<0.00005), independent of the system used to classify MDS (FAB or WHO). Moreover, elevated LDH was found to be a significant predictor of poor survival within each IPSS risk group and within each FAB group except RAEB-T. To exploit these results for refined prognostication, each IPSS risk group was split into two separate categories (A=normal LDH vs B=elevated LDH). Using this LDH-assisted approach, it was possible to identify MDS patients with unfavorable prognosis within the low and intermediate IPSS risk groups. We propose that the IPSS+LDH score should improve clinical decision-making and facilitate proper risk stratification in clinical trials.

The myelodysplastic syndrome(s): a perspective and review highlighting current controversies

The myelodysplastic syndrome (MDS) includes a diverse group of clonal and potentially malignant bone marrow disorders characterized by ineffective and inadequate hematopoiesis. The presumed source of MDS is a genetically injured early marrow progenitor cell or pluripotential hematopoietic stem cell. The blood dyscrasias that fall under the broad diagnostic rubric of MDS appear to be quite heterogeneous, which has made it very difficult to construct a coherent, universally applicable MDS classification scheme. A recent re-classification proposal sponsored by the World Health Organization (WHO) has engendered considerable controversy. Although the precise incidence of MDS is uncertain, it has become clear that MDS is at least as common as acute myelogenous leukemia (AML). There is considerable overlap between these two conditions, and the former often segues into the latter; indeed, the distinction between AML and MDS can be murky, and some have argued that the current definitions are arbitrary. Despite the discovery of several tantalizing pathophysiological clues, the basic biology of MDS is incompletely understood. Treatment at present is generally frustrating and ineffective, and except for the small subset of patients who exhibit mild marrow dysfunction and low-risk cytogenetic lesions, the overall prognosis remains rather grim. In this narrative review, we highlight recent developments and controversies within the context of current knowledge about this mysterious and fascinating cluster of bone marrow failure states.

The WHO classification of MDS does make a difference

The purpose of this study was to determine the facility and reliability of the World Health Organization (WHO) classification of myelodysplastic syndromes (MDSs) with several observers reviewing the same diagnostic specimens. We also wanted to determine if the WHO classification provided additional information about predictability of clinical response outcome. To accomplish these goals we reviewed 103 previously diagnosed cases of low-risk MDS. We found 92% interobserver agreement (P <.001). Sixty-four of these patients had been entered into clinical trials using growth factors by the Nordic MDS Study Group. The WHO classification reliably predicted therapeutic response to the combination of granulocyte colony-stimulating factor (G-CSF) and erythropoietin (Epo). The response rate differed significantly between refractory anemia with ringed sideroblasts (RARS) and refractory anemia with multilineage dysplasia and ringed sideroblasts (RCMD/RS) with regard to therapeutic response (75% versus 9%; P =.003). Also, in the group of patients with less than 5% marrow blasts, there was a difference in median survival between patients with unilineage dysplasia (51% surviving at 67 months) and those with multilineage dysplasia (median survival, 28.5 months; P =.03).

Myelodysplastic syndrome is not merely "preleukemia"

Myelodysplastic syndrome (MDS) is a disease characterized by ineffective hematopoiesis. There are significant biologic and clinical differences between MDS and acute myeloid leukemia (AML). We studied a cohort of 802 patients, 279 (35%) with newly diagnosed MDS and 523 (65%) with newly diagnosed AML, and compared clinical and biologic characteristics of the 2 groups. Complete clinical and cytogenetic data were available on all patients, and a subgroup of patients was studied for apoptosis, angiogenesis, proliferation, and growth factors. Our results demonstrate that MDS is a discrete entity that is different from AML and is characterized primarily by increased apoptosis in early and mature hematopoietic cells. Using cell sorting and loss of heterozygosity, we demonstrate that the leukemic cells from MDS patients are capable of differentiation into mature myeloid cells and monocytes. We also demonstrate that there is a significant overlap between AML and MDS when MDS is defined on the basis of an arbitrary percentage of blasts of 20% or 30%. These data suggest that despite similarities between AML and MDS in their responses to treatment and outcomes, MDS is biologically and clinically different from AML and should not be considered an early phase of AML. The data indicate that MDS must be better defined on the basis of its biology rather than the percentage of blasts; further, the data suggest that there is a need to develop therapeutic approaches that specifically address the biologic abnormalities of MDS.

Hepcidin levels and their determinants in different types of myelodysplastic syndromes

Iron overload may represent an additional clinical problem in patients with Myelodysplastic Syndromes (MDS), with recent data suggesting prognostic implications. Beyond red blood cells transfusions, dysregulation of hepcidin, the key iron hormone, may play a role, but studies until now have been hampered by technical problems. Using a recently validated assay, we measured serum hepcidin in 113 patients with different MDS subtypes. Mean hepcidin levels were consistently heterogeneous across different MDS subtypes, with the lowest levels in refractory anemia with ringed sideroblasts (RARS, 1.43 nM) and the highest in refractory anemia with excess blasts (RAEB, 11.3 nM) or in chronic myelomonocytic leukemia (CMML, 10.04 nM) (P = 0.003 by ANOVA). MDS subtypes remained significant predictors of hepcidin in multivariate analyses adjusted for ferritin and transfusion history. Consistently with current knowledge on hepcidin action/regulation, RARS patients had the highest levels of toxic non-transferrin-bound-iron, while RAEB and CMML patients had substantial elevation of C-Reactive Protein as compared to other MDS subtypes, and showed lost of homeostatic regulation by iron. Growth differentiation factor 15 did not appear as a primary hepcidin regulator in this series. If confirmed, these results may help to calibrate future treatments with chelating agents and/or hepcidin modulators in MDS patients.

Myelodysplastic syndromes: a study of 101 cases according to the FAB classification

The myelodysplastic syndromes (MDS) are a group of closely related disorders characterized by chronic cytopenias with cellular marrow, poor prognosis and refractoriness to treatment. We studied 101 consecutive cases of MDS diagnosed over a 7-year period. Peripheral blood (PB) and bone marrow (BM) samples were reviewed and classified according to the proposals of the French-American-British (FAB) cooperative group for MDS. The combined analysis of the initial laboratory features and qualitative haematological abnormalities readily allowed the distinction between the different subgroups. Thirty-two of 79 cases (40.5%) evolved towards other diseases, frequently acute leukaemia (24/79, 30%), or transformed into other MDS (7/79, 9%). In five cases, initially classified as refractory anaemia (RA) or refractory anaemia with ring sideroblasts (RAS), a transitory change to another type of MDS--two chronic myelomonocytic leukaemias (CMML), two refractory anaemias with excess of blasts (RAEB) and one refractory anaemia with excess of blasts 'in transformation' (RAEB-t)--was observed before the evolution towards acute leukaemia. This provides a new link between all these syndromes and increases the number of transitions to other MDS. Overall prognosis was very poor, with differences between subgroups. RA had the best prognosis whereas RAEB-t had the worst one. This study shows that the FAB classification is readily usable and defines well-characterized subgroups of MDS, although there are frequent transitional forms, and as the natural history of the MDS unfolds they may convert into another. The actual poor prognosis and the frequent evolution towards acute leukaemia makes necessary to investigate new methods of treatment for these disorders.

Negative regulators of hemopoiesis and stroma function in patients with myelodysplastic syndrome

The mechanism that leads to hemopoietic failure in patients with myelodysplastic syndrome (MDS) is not well understood. There is evidence, however, that regulatory molecules such as tumor necrosis factor (TNF)-alpha, Fas (CD95), and Fas-ligand, which negatively affect hemopoiesis by way of apoptosis are upregulated. Here we analyzed marrow samples from 80 patients with MDS in regard to TNF-alpha and Fas-ligand levels and a possible correlation with various disease parameters and risk factors. TNF-alpha levels were elevated in comparison to samples from normal marrow donors, however, no significant correlation with FAB subtype, cytogenetic risk group or score by the International Prognostic Scoring System (IPSS) was observed. However, there was an inverse correlation between the cytogenetic risk category (low, intermediate, high) and levels of soluble Fas-ligand. The major source of TNF-alpha were mononuclear (non-stromal) cells which appeared to produce TNF-alpha at maximum levels. Limiting dilution analysis of CD34+ precursor cells showed that individually assayed cells, removed from companion cells that presumably provided negative signals such as TNF-alpha or Fas-ligand, were able to generate progressively increasing numbers of colonies. Stromal layers derived from MDS marrow did not have an inhibitory effect. In fact, higher colony numbers were obtained from both normal and MDS marrow derived hemopoietic precursors propagated on irradiated stromal layers from MDS marrow than on stromal layers from normal marrow. These results show that substantial numbers of normal hemopoietic precursors persist in MDS marrow. However, differentiation into mature cells is inhibited by negative signals originating from accessory or abnormal hemopoietic precursors in the non-adherent marrow fraction.

Flow cytometry evaluation of erythroid dysplasia in patients with myelodysplastic syndrome

Erythroid dysplasia is the pathologic hallmark of myelodysplastic syndromes (MDS). To develop a quantitative flow-cytometry approach to its evaluation, we analyzed the expression of CD71, CD105, cytosolic H-ferritin (HF), cytosolic L-ferritin (LF) and mitochondrial ferritin (MtF) in erythroblasts from 104 MDS patients, 69 pathologic control patients and 19 healthy subjects. Six-parameter, 4-color flow cytometry was employed, and data were expressed as mean fluorescence intensity. Compared with pathologic and healthy controls, MDS patients had higher expression of HF (P < 0.001) and CD105 (P < 0.001), and lower expression of CD71 (P < 0.001). MtF was specifically detected in MDS with ringed sideroblasts, and there was a close relationship between its expression and Prussian blue staining (r = 0.89, P < 0.001). In vitro cultures of myelodysplastic hematopoietic progenitors showed that both HF and MtF were expressed at a very early stage of erythroid differentiation, and that MtF expression is specifically related to mitochondrial iron loading. A classification function based on expression levels of HF, CD71 and CD105 allowed us to correctly classify > 95% of MDS patients. This flow-cytometry approach provides an accurate quantitative evaluation of erythroid dysplasia and allows a reliable diagnosis of sideroblastic anemia, and may therefore be a useful tool in the work-up of patients with MDS.