Richard D. Brunning

The 2008 revision of the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia: rationale and important changes

Recently the World Health Organization (WHO), in collaboration with the European Association for Haematopathology and the Society for Hematopathology, published a revised and updated edition of the WHO Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The 4th edition of the WHO classification incorporates new information that has emerged from scientific and clinical studies in the interval since the publication of the 3rd edition in 2001, and includes new criteria for the recognition of some previously described neoplasms as well as clarification and refinement of the defining criteria for others. It also adds entities-some defined principally by genetic features-that have only recently been characterized. In this paper, the classification of myeloid neoplasms and acute leukemia is highlighted with the aim of familiarizing hematologists, clinical scientists, and hematopathologists not only with the major changes in the classification but also with the rationale for those changes.

Virus-associated hemophagocytic syndrome: a benign histiocytic proliferation distinct from malignant histiocytosis.

Nineteen patients whose bone marrow smears showed histiocytic hyperplasia with prominent hemophagocytosis were found to have a clinicopathologic syndrome associated with active viral infection. High fever, constitutional symptoms, liver function, and coagulation abnormalities and peripheral blood cytopenias were characteristic findings. Hepatosplenomegaly, lymphadenopathy, bilateral pulmonary infiltrates, and skin rash were often present. Fourteen of the patients were immunosuppressed. Active infection by herpes group viruses was documented in 14 patients and by adenovirus in 1. The bone marrow of most patients also showed decreased granulopoiesis and erythropoiesis with normal to increased numbers of megakaryocytes. Treatment generally consisted of supportive therapy and withdrawal of immunosuppressive drugs. Thirteen patients recovered. Lymph node biopsy and autopsy material showed generalized histiocytic hyperplasia with hemophagocytosis. The relationship of this disorder to familial hemophagocytic reticulosis, familial erythrophagocytic lymphohistiocytosis, histiocytic medullary reticulosis, and malignant histiocytosis is discussed. Immunosuppressive and cytotoxic therapy may be contraindicated in the treatment of this virus‐associated syndrome.

Report of the National Cancer Institute-sponsored workshop on definitions of diagnosis and response in acute myeloid leukemia.

The National Cancer Institute (NCI) sponsored a workshop to develop a set of standardized diagnostic and response criteria for acute myeloid leukemia (AML) clinical trials. The French-American-British (FAB) classification was retained for diagnosing AML, with the addition of patients with bone marrow morphologic features of a myelodysplastic syndrome and less than 30% bone marrow blasts, but with greater than or equal to 30% blasts in the peripheral blood. In this report, there are four important subgroups of AML not defined in the FAB classification that are discussed: undifferentiated acute leukemia, MO (AML lacking definitive myeloid differentiation by morphology or conventional cytochemistry but with ultrastructural or immunophenotypic evidence for AML), mixed lineage leukemia, and hypocellular AML. Definitions of response for clinical trials are presented to facilitate comparisons among different studies. Complete remission is considered the only response worth reporting in phase III trials, since lesser responses do not improve survival. Partial remissions may be of interest to identify active new agents in phase I and II studies. Monoclonal antibodies and cytogenetic studies are not part of the routine assessment of remission or reassessment at relapse, and their role in the evaluation of patients with AML is currently being evaluated in clinical trials. Although we recognize that some of the definitions in this report are arbitrary, generalized use of these guidelines will make results of clinical trials more comparable and interpretable.

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.

Diagnosis and classification of myelodysplastic syndrome: International Working Group on Morphology of myelodysplastic syndrome (IWGM-MDS) consensus proposals for the definition and enumeration of myeloblasts and ring sideroblasts

This article details the proposals of the IWGM-MDS for the definition of myeloblasts, promyelocytes and ring side-roblasts in patients with myelodysplastic syndrome. The classification of myelodysplastic syndromes is based on the morphological criteria proposed by the French-American-British (FAB) and World Health Organization (WHO) groups. Accurate enumeration of blast cells, although essential for diagnosis of myelodysplastic syndrome and for assignment to prognostic groups, is often difficult, due to imprecise criteria for the morphological definition of blasts and promyelocytes. An International Working Group on Morphology of Myelodysplastic Syndrome (IWGM-MDS) of hematopathologists and hematologists expert in the field of myelodysplastic syndrome reviewed the morphological features of bone marrows from all subtypes of myelodysplastic syndrome and agreed on a set of recommendations, including recommendations for the definition and enumeration of blast cells and ring sideroblasts. It is recommended that (1) agranular or granular blast cells be defined (replacing the previous type I, II and III blasts), (2) dysplastic promyelocytes be distinguished from cytologically normal promyelocytes and from granular blast cells, (3) sufficient cells be counted to give a precise blast percentage, particularly at thresholds that are important for diagnosis or prognosis and (4) ring sideroblasts be defined as erythroblasts in which there are a minimum of 5 siderotic granules covering at least a third of the nuclear circumference. Clear definitions and a differential count of a sufficient number of cells is likely to improve precision in the diagnosis and classification of myelodysplastic syndrome. Recommendations should be applied in the context of the WHO classification.

High-Resolution Chromosomes as an Independent Prognostic Indicator in Adult Acute Nonlymphocytic Leukemia

Using high-resolution chromosomes of bone-marrow specimens from 105 consecutive adult patients with de novo acute nonlymphocytic leukemia, we found an unusually high degree of complexity in this disorder, which may explain previous difficulties in identifying useful prognostic indicators. Specimens from 99 of the 105 patients were successfully analyzed, and 92 (93 per cent) had a chromosomal defect. Seventeen categories were identified, 12 representing a specific recurrent defect. Three of them have been found to have independent prognostic importance. Patients with an inversion 16 (9 per cent), diagnosed as having M2, M4, or M5b disease according to the morphologic classification of the French-American-British Acute Leukemia Cooperative Study Group, had a uniform and sustained complete remission and a median survival of 25 months. In contrast, 14 patients (14 per cent) with complex chromosomal abnormalities and a diagnosis of M1, M2, M4, M5a, or M6 disease had a very poor prognosis. In 12 of the 14 patients efforts to achieve induction of remission failed, and the group had a median survival of 2.5 months. A third group with a trisomy 8 as the single defect (11 per cent) had an intermediate prognosis and a median survival of 10 months. With the different types of treatment for acute nonlymphocytic leukemia that are now available, we suggest that high-resolution chromosome analysis will become an important tool in selecting specific types of therapy for groups of patients with differing prognoses.

Bilateral trephine bone marrow biopsies in lymphoma and other neoplastic diseases.

We have evaluated the usefulness of bilateral rather than unilateral posterior iliac spine trephine biopsies in searching for lymphoma and other neoplastic diseases in the bone marrow. Two hundred and eighty-two patients with these diseases were studied. Tumor was found on only one side in 22% of patients with non-Hodgkins malignant lymphoma, in 43% of patients with Hodgkins disease, and in 36% of patients with other neoplastic processes. Thus, the second biopsy yields an additional 11% to 22% of positive biopsies. We conclude that bilateral trephine bone marrow biopsies should be routinely performed when searching for tumor in the bone marrow.

Chronic lymphoproliterative disorder with unusual clinical, morphologic, ultrastructural and membrane surface marker characteristics

Four of 105 patients with chronic lymphocytic leukemia (CLL) manifested clinical, morphologic, ultrastructural and membrane surface marker characteristics that differed from those found in patients with typical CLL of demonstrated B-lymphocyte origin. These four patients presented with moderate increases in absolute lymphocyte counts, absolute neutropenia, polyclonal hypergammaglobulinemia and hepatosplenomegaly without lymphadenopathy. Two of them were unusually young, 19 and 25 years old, at the time of diagnosis. The proliferating lymphocytes carried receptors for sheep erythrocytes, a T-lymphocyte marker. In the three patients tested, the lymphocytes also carried Fc receptors. Ultrastructurally the lymphocytes contained cytoplasmic inclusion bodies consisting of parallel tubular arrays. The parallel tubular arrays corresponded to prominent cytoplasmic azurophilic granules on light microscopy. Parallel tubular arrays were found in less than 1 per cent of the lymphocytes in eight patients with typical B-lymphocyte CLL. The process in these four patients may be a distinctive chronic lymphoproliferative disorder originating in T lymphocytes with Fc receptors found in small numbers in the blood of normal persons.

Bacteria‐associated hemophagocytic syndrome

Histiocytic medullary reticulosis (HMR) was originally defined as a neoplastic disorder. Some cases reported as HMR have been characterized by a systemic proliferation of mature histiocytes showing hemophagocytosis, bone marrow necrosis, pancytopenia, hepatitis, and coagulopathy. Clinically, these patients have fever and constitutional symptoms and often have hepatosplenomegaly and lymphadenopathy. Although there is a high mortality rate, this process appears to be reactive and has been associated with active viral infection. Similar cases have been briefly described that were associated with other agents or disease processes, but concomitant viral infections were not excluded. Three characteristic examples of this hemophagocytic syndrome that were associated with bacterial sepsis are described. Active infection by those viruses that have previously been associated with the syndrome was excluded. It appears that the hemophagocytic syndrome may be associated with various types of active disseminated infections.

The value of anti-pax-5 immunostaining in routinely fixed and paraffin-embedded sections: a novel pan pre-B and B-cell marker.

Whereas L26 (anti-CD20) is well established as a B-cell marker of high specificity for use in paraffin-embedded tissues and JCB117 (anti-CD79a) is increasingly used, a comparable additional pan-B-cell antibody has hitherto not yet been identified. Here we have studied the use of a novel anti-pan-B-cell marker Pax-5 for use in diagnostic pathology. Pax-5 encodes for BSAP (Pax-5), a B-cell-specific transcription factor, the expression of which is detectable as early as the pro-B-cell stage and subsequently in all further stages of B-cell development until the plasma cell stage where it is downregulated. Pax-5 is essential for B-lineage commitment in the fetal liver, whereas in adult bone marrow this transcription factor is required for progression of B-cell development beyond the early pro-B (pre-BI) cell stage. Among the B-cell genes that are present in early B-cell development and are upregulated by Pax-5 are CD19 and Ig&agr; (CD79a). We have tested a commercially available anti-Pax-5 antibody (anti-BSAP, clone 24) in a series of 592 routinely fixed and paraffin wax-embedded biopsies, including lymph nodes, bone marrow, and various other organs containing lymphoid tissues. Pax-5 protein (BSAP) was detected in all cases of precursor and mature B-cell non-Hodgkin lymphomas/leukemias. In addition, in 97% of classic Hodgkin lymphomas, Reed-Sternberg cells expressed Pax-5. However, Pax-5 was not detected in any of the multiple myelomas, solitary plasmacytomas, and 4% of diffuse large B-cell lymphomas. Among those diffuse large B-cell lymphomas not expressing Pax-5 were only those with terminal B-cell differentiation. All T-cell non-Hodgkin lymphomas, including ALCL and lymphoblastic lymphomas and leukemias, were negative. There was a strong association between Pax-5 and CD20 expression. We conclude that anti-Pax-5 is an excellent pan-B and pan-pre-B-cell marker. We have found that anti-Pax-5 is superior to anti-CD20 in the diagnosis of pre-B acute lymphoblastic leukemia and classic Hodgkin lymphoma versus ALCL of T and “null” cell type. It was also useful in differential diagnosis between lymphoplasmacytic lymphoma and plasmacytoma. Even though there is an excellent correlation between CD20 and Pax-5 expression, anti-Pax-5 exceeds the specificity and sensitivity of L26 (anti-CD20) because of its earlier expression in B-cell differentiation and its ability to detect all committed B cells, including classic Hodgkin lymphoma.