The 2016 revision of the World Health Organization classification of lymphoid neoplasms.

A revision of the nearly 8-year-old World Health Organization classification of the lymphoid neoplasms and the accompanying monograph is being published. It reflects a consensus among hematopathologists, geneticists, and clinicians regarding both updates to current entities as well as the addition of a limited number of new provisional entities. The revision clarifies the diagnosis and management of lesions at the very early stages of lymphomagenesis, refines the diagnostic criteria for some entities, details the expanding genetic/molecular landscape of numerous lymphoid neoplasms and their clinical correlates, and refers to investigations leading to more targeted therapeutic strategies. The major changes are reviewed with an emphasis on the most important advances in our understanding that impact our diagnostic approach, clinical expectations, and therapeutic strategies for the lymphoid neoplasms.

[Overview of lymphoid neoplasms in the fourth edition of the WHO classification].

The fourth edition of the "WHO Classification of Tumours of Haematopoietic and Lymphoid tissues" was published in 2008 as an updated version of the third edition published in 2001. In this review, the revised points in the lymphoid neoplasms in the fourth edition were summarized from the viewpoint of doctors and medical technologists in clinical laboratories in hospitals. The diseases are classified based on information about morphology, immunophenotype, genetic features, and clinical features. B lymphoblastic leukemia/lymphoma with 7 recurrent genetic abnormalities is individually classified as a provisional entity. Anaplastic large cell lymphoma is divided into two entities, ALK positive and ALK-negative. The pathogenesis of the former is involved with ALK gene rearrangement with several partner genes. Two borderline categories between diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma, and between DLBCL and classical Hodgkin lymphoma are newly recognized as a distinct disease entity based on the overlapping morphological and genetic features. In the diagnosis of lymphoid neoplasms, understanding the morphological features is fundamental. On the other hand, the importance of immunohistochemistry and flow cytometry to clarify the immunophenotype, and chromosomal analysis and genetic examination to clarify the genetic features has been raised.

[State of medical care of patients with hematological malignancies in Kyïv].

In the article data are presented about morbidity by oncogematologic pathology - one of the most meaningful of social-economic problems. In Ukraine annually diagnose the to 8 thousand new cases of haemoblastosis. Indexes of morbidity on a 100 thousand population are 5,2; at illness of Hodgkin's lymphoma - 2,5, at plural myeloma - 1,6; at leukemia - 8,1. Morbidity by haematological pathology in Kyiv long time remains high: annually 250 expose patients with malignant lymphnoma, 57 - with myeloma, 190 - with leukemia, from them at 55 % is a sharp form and at 40 % - chronic. The anxiety of doctors causes circumstance that the special treatment is overcome 58,1 % patients by leukemia, 68,6 % - plural myeloma and 77,8 % patients with malignant lymphoma. World experience shows that application of complex methods of therapy allows to prolong life-span 80-90 % patients with Hodgkin's malignant lymphoma on 10, and at 95 % patients by a lymphogranulomatosis - to attain nonrecurrence survival to 5 years.

Impact of Genetics on Mature Lymphoid Leukemias and Lymphomas.

Recurrent genetic aberrations have long been recognized in mature lymphoid leukemias and lymphomas. As conventional karyotypic and molecular cloning techniques evolved in the 1970s and 1980s, multiple cytogenetic aberrations were identified in lymphomas, often balanced translocations that juxtaposed oncogenes to the immunoglobulin (IG) or T-cell receptor (TR) loci, leading to dysregulation. However, genetic characterization and classification of lymphoma by conventional cytogenetic methods is limited by the infrequent occurrence of recurrent karyotypic abnormalities in many lymphoma subtypes and by the frequent difficulty in growing clinical lymphoma specimens in culture to obtain informative karyotypes. As higher-resolution genomic techniques developed, such as array comparative genomic hybridization and fluorescence in situ hybridization, many recurrent copy number changes were identified in lymphomas, and copy number assessment of interphase cells became part of routine clinical practice for a subset of diseases. Platforms to globally examine mRNA expression led to major insights into the biology of several lymphomas, although these techniques have not gained widespread application in routine clinical settings. With the advent of next-generation sequencing (NGS) techniques in the early 2000s, numerous insights into the genetic landscape of lymphomas were obtained. In contrast to the myeloid malignancies, most common lymphomas exhibit an at least somewhat mutationally complex genome, with few single driver mutations in the majority of patients. However, many recurrently mutated pathways have been identified across lymphoma subtypes, informing targeted therapeutic approaches that are beginning to make meaningful changes in the treatment of lymphoma. In addition to the ability to identify possible therapeutic targets, NGS techniques are highly amenable to the tracking of residual lymphoma following therapy, because of the presence of unique genetic "fingerprints" in lymphoma cells due to V(D)-J recombination at the antigen receptor loci. This review will provide an overview of the impact of novel genetic technologies on lymphoma classification, biology, and therapy.

Role of CD71 in acute leukemia- An immunophenotypic marker for erythroid lineage or proliferation?

BACKGROUND: CD71 or Transferrin receptor is expressed on the surface of erythroid lineage cells. CD71 expression has been found to be significantly increased in rapidly proliferating cells. METHODS: This cross-sectional study included 37 bone marrow samples of acute leukemia cases diagnosed between October 2016 to April 2018. The samples were analysed on BD FACS Canto II. We evaluated the expression of CD71 on leukemic blasts and compared median fluorescent intensities (MFI) of blasts in different types of acute leukemias. RESULTS: The 37 cases comprised of 21 Acute Myeloid Leukemia (AML), 13 B-Acute Lymphoblastic Leukemia (B-ALL), 2 T- Acute Lymphoblastic Leukemia (T-ALL) and 1 mixed phenotypic acute leukemia (MPAL), T/Myeloid. CD 71 expression was noted in 70.3% (n= 26/37) of acute leukemia cases. CD71 expression was most commonly observed in AML (n= 15/21;71.4%), followed by B-ALL (n= 9/13;69.2%) and T-ALL (n= 1/2;50%). Single case of MPAL revealed blasts positive for CD71. MFI of leukemic blasts of single CD71 positive T-ALL was found to be highest, followed by AML, MPAL (T/Myeloid) and least in B ALL. Of the AML cases, the blasts of AML-M6, acute promyelocytic leukemia and AML-M1 showed higher CD71 expression in terms of MFI. CONCLUSIONS: Surface CD71 expression is not only found in erythroid lineage cells, but also in proliferating cells. CD71 MFI is highest in T lymphoblasts followed by leukemic erythroblasts, myeloblasts and least in B lymphoblasts.

T gamma (T gamma) cells suppress growth of erythroid colony-forming units in vitro in the pure red cell aplasia of B-cell chronic lymphocytic leukemia.

In vitro studies were performed in two patients with B-cell chronic lymphocytic leukemia who developed pure red cell aplasia (CLL-PRCA). During the active phase of their red cell aplasia, there was a marked reduction in the numbers of erythroid colony-forming units (CFU-E). Unfractionated sera or separated IgG fractions from these patients did not impair CFU-E proliferation from either autologous or allogeneic marrows. Increased numbers of T lymphocytes were present in marrow aspirates of these patients. Analysis of these T cells indicated that 90 and 35%, respectively, bore Fc receptors for IgG (T gamma cells). Removal of T cells by E-rosetting techniques augmented CFU-E growth in CLL-PRCA 10-fold. Similar treatment of normal marrows did not cause similar enhanced growth of CFU-E. Co-cultures of marrow T cells or T gamma cells obtained during the active phase of CLL-PRCA suppressed CFU-E growth from autologous or allogeneic marrows. After achieving drug-induced remission of the PRCA, marrow T cells were no longer inhibitory. In contrast, BFU-E (erythroid burst-forming units) or granulocyte proliferation in diffusion chambers were not suppressed by CLL-PRCA T cells. These findings suggest that the development of PRCA in B-cell CLL may result from suppression of CFU-E proliferation by T gamma cells.

Precursor T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma and acute biphenotypic leukemias.

Session 4 of the 2005 Society of Hematopathology/European Association for Haematopathology Workshop focused on case presentations of precursor T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma (pre-T ALL/LBL) and acute biphenotypic leukemia. Pre-T ALL represents approximately 15% of childhood and 25% of adult ALL cases. Pre-T LBL comprises 85% to 90% of LBL and frequently manifests as a mediastinal mass. Gene expression studies have shown distinct subtypes of LYL1+, HOX11+, TAL1+, and MLL+ pre-T ALL/LBL. HOX11 overexpression may correlate with a good prognosis in adult pre-T ALL. ABL gene amplification and NOTCH1 gene mutations in subsets of pre-T ALL/LBL suggest patients may benefit from therapy with tyrosine kinase and gamma-secretase inhibitors, respectively. Acute biphenotypic leukemias are characterized by a single population of blasts that express myeloid, T- or B-lineage antigens in various combinations and account for fewer than 4% of all acute leukemias. The blasts have a high incidence of chromosome abnormalities. An accurate diagnosis of pre-T ALL/LBL and acute biphenotypic leukemia requires a multiparametric approach, including examination of morphologic features, immunophenotype, clinical characteristics, and cytogenetic and molecular findings.

Distribution and clinicopathologic characteristics of non-Hodgkin's lymphoma in India: a study of 935 cases using WHO classification of lymphoid neoplasms (2000).

The frequency of various subtypes of non-Hodgkin's lymphoma (NHL) differs in various regions worldwide. We studied distribution of various subtypes of NHL by using WHO classification of lymphoid neoplasms (2000), immunophenotyping and clinicopathologic characteristics of various histologic subtypes in 935 cases. B- and T-cell NHL constituted 79.3% and 18.8% of cases. Diffuse large B-cell lymphoma (DLBL) was the most common subtype (50.2%). A lower frequency of follicular lymphoma, marginal zone lymphoma and mantle cell lymphoma (MCL) was noted compared to that observed in the developed countries, whereas a lower frequency of peripheral T-cell lymphoma - not otherwise specified (PTCL-NOS) and extranodal NK/T-cell lymphoma was seen compared to that in the other Asian countries. A higher frequency of DLBL and precursor T-lymphoblastic leukemia/lymphoma was noted. Extranodal and bone marrow involvement in MCL and PTCL-NOS was less frequent. Anaplastic variant of DLBL was noted in 21.5% of all DLBLs. Null/T-cell anaplastic large cell lymphoma presented in the older age.

Having a higher blast percentage in circulation than bone marrow: clinical implications in myelodysplastic syndrome and acute lymphoid and myeloid leukemias.

Determining the percentage of peripheral blood (PB) and bone marrow (BM) blasts is important for diagnosing and classifying acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). Although most patients with acute leukemia or MDS have a higher percentage of BM blasts than PB blasts, the relative proportion is reversed in some patients. We explored the clinical relevance of this phenomenon in MDS (n = 446), AML (n = 1314), and acute lymphoblastic leukemia (ALL) (n = 385). Among patients with MDS or ALL, but not AML, having a higher blast percentage in PB than in BM was associated with significantly shorter survival. In multivariate analyses, these associations were independent of other relevant predictors, including cytogenetic status. Our findings suggest that MDS and ALL patients who have a higher percentage of PB blasts than BM blasts have more aggressive disease. These data also suggest that MDS classification schemes should take into account the percentage of blasts in PB differently from the percentage of blasts in BM.

Childhood lymphoblastic cancer: subgroups defined by nonhuman primate antisera to human lymphatic leukemia cell antigens.

Lymphoblasts from 23 children with acute lymphocytic leukemia (ALL) and 10 with lymphoblastic lymphoma (LBL) were studied by complement-dependent microcytoxicity tests with two nonhuman primate antisera defining leukemia-associated and lymphoma-associated antigens. Cells form 15 patients with ALL and 1 with LBL reacted only with antiserum to chronic lymphatic leukemia (CLL). These group-I patients were predominantly female. Most were pancytopenic and lacked mediastinal widening and T-cell markers; lymphoblasts from 15 were periodic acid-Schiff-positive. Cells from 8 male patients reacted only with antiserum to converted lymphosarcoma (LS). All these group-II patients expressed T-cell markers; 5 had mediastinal enlargement and 2, an abdominal mass. Six of the 8 were PAS-negative. Cells from 9 patients reacted with both antisera. The group-III patients demonstrated some characteristics of each of the above groups. Patients whose lymphoblasts reacted with CLL antiserum presented with clinical and laboratory features indicative of a good prognosis, i.e., ALL with PAS positivity and no T-cell markers or localized mass. Patients whose cells reacted with LS antiserum often had bad prognostic features: mediastinal or abdominal mass, expression of T-cell markers, and PAS negativity. These antisera appear able to differentiate childhood ALL from LBL. The distinction is important prognostically and perhaps therapeutically.

Classification of human leukemia by membrane antigen analysis with xenoantisera.

Rabbit and monkey antisera after appropriate absorption were rendered specific for normal or leukemic lymphoid- and myeloid-associated antigens. Antisera defining a common peripheral blood T-cell antigen, a thymus leukemia antigen, HLA-DR or Ia-like antigen, common acute lymphoblastic leukemia antigen (CALLA), and a myeloid-monocyte (M) antigen were used in a microcytotoxicity assay to classify leukemic cells from 30 patients in a double blind study. The antisera to the M antigen reacted with adherent peripheral blood cells and polymorphonuclear leukocytes and failed to react with nonadherent mononuclear cells and enriched T-cells and chronic lymphocytic leukemia cells. The M antisera also reacted with U937, a monocytic-type cell line, and with HL60, a promyelocytic-type cell line, but failed to react with T and B lymphoblastoid cell lines. The specificities of the other antisera have been described in previous reports. Cells from three of the patients could not be phenotyped by microcytotoxicity testing. Cells from 25 patients had a consensus morphological or histochemical diagnosis of either acute lymphoblastic leukemia or acute nonlymphocytic leukemia. The serological classification of these patients using the five types of antisera listed above were consistent with the consensus diagnosis. In addition, the lymphoid cancers were further subclassified as to T-, B-, or thymus antigen types. There was no consensus lymphoid versus myeloid diagnosis on cells from two patient. The serological classification in both cases favored a diagnosis of myeloid rather than lymphoid leukemia.

Definition of the high-risk acute lymphoblastic leukemia patient by immunological phenotyping with monoclonal antibodies.

An accurate method of classification of the surface membrane characteristics of blast cells from patients with acute lymphoblastic leukemia would allow a more definitive study of the nature of this disease. Monoclonal antibodies have been produced to the surface antigens of leukemic blasts form a patient with high-risk acute lymphoblastic leukemia. Two antibodies of interest were obtained from this immunization. These two, in combination with a monoclonal antibody with anti-Ia specificity, have been used to obtain surface phenotypes for patients with childhood acute lymphoblastic leukemia. Preliminary results indicate that the definition of a high-risk group, using these antibodies, possible.

Immunological definition of leukemic cell surface phenotypes.

Immunological phenotyping of blasts from over 200 children with acute lymphocytic leukemia (ALL) reveals both interpatient differences and phenotypic heterogeneity in the blast population from individual patients. A battery of five independent lymphocyte differentiation markers, erythrocyte-forming rosettes. T-cell antigens, Ia-like antigens, the common ALL antigen, and surface immunoglobulin, permit classification of all ALL specimens into four major marker groups. These are common, T-cell, B-cell, and undifferentiated ALL. Heterogeneity in the marker phenotypes within each of the major groups is observed. Within individual erythrocyte receptor-positive ALL specimens, phenotypic heterogeneity in the blast population is demonstrated. Sequential determinations of the blast phenotype during periods of active disease reveal a second example of intrapatient blast cell heterogeneity. Differences in phenotype of the dominant blast populations present prior to treatment and at relapse are observed in sequential studies of individual patients. These shifts in phenotype are nonrandom. They result most frequently from losses in single differentiation markers. A unifying hypothesis which explains these observations of phenotypic heterogeneity is that ALL blasts manifest limited lymphoid-like differentiation.

Analysis of the clinical and biological significance of lymphoid phenotypes in acute leukemia.

Analysis of leukemic cell phenotypes using cell surface antigens and various enzymes indicates that acute lymphoblastic leukemia (ALL) is a biologically heterogeneous disease consisting of four major subclasses with additional subsets existing within these subclasses. These different types of ALL appear to reflect sequential stages of early lymphocyte ontogeny. There is a strong association between cell phenotype and first remission duration in ALL (p trend less than 0.0001) and an equally strong correlation between remission duration and white blood cell count at presentation. If common ALL and thymic ALL (T-ALL) are compared after adjustment of white blood cell counts, then the prognostic differences between these two major subclasses almost disappear (p = 0.38). It is suggested, therefore, that an immunological (and enzymatic) phenotype of ALL subclasses may not be an independent correlate of prognosis but nevertheless is linked to other differentiation-linked features, especially growth rate and sites of clonal expansion (e.g., marrow versus thymus), which critically influence the size of the clonogenic leukemic population and its associated evolutionary status with respect to drug resistant mutants at the time of diagnosis and introduction of therapy. An extensive library of monoclonal antibodies has been used to further define the phenotypic heterogeneity of T-and non-T All. Several of the antigenic structures identified by these monoclonal antibodies have been isolated and characterized. T-ALL can be dissected into several subsets corresponding to stages of intrathymic differentiation. Non-T ALL (null-ALL, common ALL, and B-ALL) all have a phenotype indicative of B-lineage affiliation indicating that "non-T, non-B" ALL may originate from B-cell precursors in bone marrow. A cell type is identified in normal bone marrow which has the same identical monoclonal antibody-defined phenotype as common ALL and may provide the target cell for this disease.

Use of monoclonal antibodies, morphology, and cytochemistry to probe the cellular heterogeneity of acute leukemia and lymphoma.

A combined immunological, morphological, and cytochemical approach to the study of malignant cells in patients with acute leukemia and lymphoma is presented. Newly produced monoclonal antibodies that bind to antigens of human mononuclear cells (TA-1), or B-lymphocytes (BA-1) were used to study malignant cells from patients with acute lymphoblastic leukemia (ALL). acute myelocytic leukemia, acute myelomonocytic leukemia, and chronic lymphocytic leukemia. Results in lymphoid leukemia-lymphoma patients were compared with other immunological markers and indicate that the major groups of ALL and childhood non-Hodgkin's lymphoma are T-ALL, pre-T-ALL, pre-B-ALL, B-ALL, and non-T, non-B-ALL. In addition, each major group had multiple phenotypes when analyzed with seven immunological markers including the erythrocyte rosette receptor, surface immunoglobulin, cytoplasmic immunoglobulin M, the early lymphocyte-acute lymphoblastic leukemia antigen, monoclonal antibody TA-1, monoclonal antibody BA-1, and a monoclonal antibody against HLA-DR. While immunological heterogeneity was demonstrable within each group, distinct biological behavior was observed, with T-ALL and B-ALL generally presenting as "lymphomas" and the others presenting as "leukemias." Morphological analysis using the French-American-British classification provided independent information in the definition of groups with differing clinical behavior. Cytochemical analyses demonstrated focal paranuclear staining of leukemia cells with acid phosphatase in 73% of T-ALLs and 6% of non-T, non-B-ALLs.

Glucocorticoid receptors in immunological subtypes of childhood acute lymphocytic leukemia cells: a Pediatric Oncology Group Study.

Glucocorticoid receptors were quantitated by a whole cell method in cells from 593 children with acute leukemia at the time of diagnosis. Leukemia cells were also immunologically typed and divided into early pre-B- (not reactive with antibodies to T-lymphocyte antigens, surface immunoglobulin-negative, cytoplasmic immunoglobulin-negative), pre-B- (not reactive with antibodies to T-lymphocyte antigens, surface immunoglobulin-negative, cytoplasmic immunoglobulin-positive), B- (not reactive with antibodies to T-lymphocyte antigens, surface immunoglobulin-positive), and T- (reactive with antibodies to T-lymphocyte antigens) subtypes. There was a median of 9.7 X 10(3) sites per cell in the 359 with early pre-B-acute lymphocytic leukemia, a median of 8.1 X 10(3) sites per cell from 103 patients with pre-B-cell leukemia, and a median of 4.0 X 10(3) sites per cell from 116 patients with T-cell leukemia. The distributions per cell were significantly different among these 3 groups (P less than 0.0001). The 15 patients with B-cell disease had a median of 3.2 X 10(3) sites per cell. At the time of analysis, remission induction data are available for most of these patients. Within the early pre-B- group 291 patients with a median receptor number of 9.9 X 10(3) achieved remission, while 13 with a median receptor number of 4.8 X 10(3) did not. These distributions were significantly different (P = 0.034). Within the pre-B- and T-cell groups the distributions of receptor numbers for responders and non-responders were not significantly different. We conclude that each immunological subtype has characteristic receptor distribution. High receptor number within the null group is associated with the ability of the patient to achieve remission; however, the range of values within each patient group is too broad to use this assay as a predictor of response for any individual patient.

A clinical perspective on cell markers in acute lymphocytic leukemia.

Two hundred consecutive new patients, with acute lymphocytic leukemia (ALL) have been studied with a battery of five cell marker assays to determine if a classification system with prognostic significance can be developed; 182 have been classified among four groups as follows: 33 T-cell, 3 B-cell, 126 common, and 20 undifferentiated ALLs. Patients with T-cell disease are likely to have unfavorable clinical prognostic features and a poor response to therapy. Rare patients with B-cell disease are closely related clinically to non-Hodgkin's lymphoma. Those with common ALL infrequently have unfavorable clinical features and have a superior outcome to that of T-cell patients. Children with undifferentiated markers seem to respond less well to treatment than do those with common ALL, yet may not be identifiable as poor risk by clinical features. What remains to be resolved with further observation is whether these marker patterns are more reliable indicators of prognosis than the usual clinical determinants predisposing to treatment failure (high white blood cell count, mediastinal mass, and central nervous system disease). At the present time, it appears that in the absence of poor-risk clinical prognostic features, patients with common ALL are more likely to have lasting remissions than those with erythrocyte-rosette-positive T-cell disease or those with ALL that is undifferentiated by markers.

Enumeration and identification of human leukemic lymphocytes by their natural binding of bacteria.

The recently described property of bacteria to bind to human lymphocytes was used to distinguish between normal and chronic leukemic lymphocyte (CLL) populations. Strains of the following bacteria were used in this study: Arizona hinshawii, Escherichia coli strains 1 and 2, Bacillus globigii, Brucella melitensis, Corynebacterium diphtheriae strains 1 and 2, Corynebacterium xerosis, Sarcina lutea, Staphylococcus aureus, and Staphylococcus epidermidis. For identification of immunoglobulin-bearing lymphocytes, a strain of E. coli that did not bind to human lymphocytes was coated with anti-human light-chain antibody. Labeling of lymphocytes with bacteria was promoted by centrifugation. In the eight CLL patients studied, in which greater than 90% of the lymphocytes were leukemic cells, 52 to 77% were labeled by anti-human light-chain antibody-E. coli, 80 to 93% were labeled by Br. melitensis, and 78 to 95% were labeled by E. coli 1 compared to 11 to 24, 11 to 22, and 30 to 44%, respectively, in normal individuals, Thus, Br. melitensis, E. coli 1, and the anti-human light-chain antibody-E. coli may have diagnostic value for CLL. The percentage of the lymphocyte population that bound each of the other bacteria varied from patient to patient. Preliminary results obtained by studying the pattern of binding of E. coli 2, B. globigii, Sa. lutea, or S. aureus by leukemic lymphocytes suggest that categories of CLL patients may be distinguished by this method.

Analysis of surface antigen profile, TdT expression, and T cell receptor gene rearrangement for maturational staging of leukemic T cells: a pediatric oncology group study.

By using monoclonal antibodies specific for T lineage surface antigens, neoplastic T cells from 53 children with T cell acute lymphoblastic leukemia and T cell non-Hodgkin's lymphoma were analyzed and assigned to phenotypically defined stages of T cell maturation. Cells were also analyzed for T cell antigen receptor beta-chain gene and immunoglobulin heavy and light chain gene rearrangements. Clonal rearrangements of T cell antigen receptor beta-chain gene and a germ-line configuration of the immunoglobulin genes were found in cells from all cases. The expression of the terminal deoxynucleotidyl transferase (TdT) in leukemic T cells was studied by both qualitative immunofluorescence and quantitative enzyme immunoassay, and the level of TdT expression was correlated with maturational stages. Lymphoblasts classified as prethymic (3 patients) did not express detectable TdT. In contrast, cells from approximately 60% of the patients with early (15 patients) or intermediate (19 patients) thymocytic phenotypes and approximately 40% of the patients with mature thymocytic phenotype (16 patients) were positive for TdT. Thus, in these leukemic clones TdT was randomly expressed and showed no correlation with maturational stage.

Genotypic characterization of common acute lymphoblastic leukemia may improve the phenotypic classification.

The reactivity of five anti-B monoclonal antibodies (McAb)-OKB2 (CD24), B4 (CD19), Leu12 (CD19), BA1 (CD24), B1 (CD20)--as well as the presence of cytoplasmic immunoglobulins (CyIg) were assessed in 100 cases of common acute lymphoblastic leukemia (cALL) at presentation (TdT+, J5 [CD10]+, HLA-Dr+). All cases studied revealed one or more B-cell related markers and a hierarchy in their expression was documented: OKB2 was positive in all cases tested (100%), B4 was expressed in 96.4% of cases, Leu12 in 95.8%, BA1 in 94.9%, B1 in 18.3%, and CyIg in 23%. Further evidence of the B-cell origin of cALL was obtained by molecular analyses at the DNA level which demonstrated the presence of an Ig heavy chain gene rearrangement in all 37 cases assessed, while 37.8% showed a light chain gene reorganization. A genomic subclassification of cALL demonstrated that the majority of cases showed an immature molecular configuration with one (8.1%) or both (54.1%) Ig heavy chain alleles rearranged and a germ-line configuration of the light chain genes; 27% revealed a heavy chain gene involvement and one k allele rearranged. Only four cases (10.8%) showed a more mature configuration with both k alleles rearranged or a gamma chain gene involvement. This study confirms that cALL is characterized by the proliferation of immature B-lineage-committed elements and indicates that the leukemic cells are blocked at different levels of B-differentiation which may be recognized with the use of multiple phenotypic or genotypic B-cell-related markers.