Neutral glycosphingolipid expression in B-cell neoplasms

The expression of neutral glycosphingolipids (GSL) in 37 B-cell neoplasms [7 acute lymphocytic leukemia (ALL), 5 Burkitt's lymphoma (BL), 7 chronic lymphocytic leukemia (CLL), 5 diffuse, poorly differentiated lymphoma (DPDL), 6 diffuse histiocytic lymphoma (DHL), 3 hairy-cell leukemia (HCL), and 4 multiple myeloma (MM)] was examined. Patterns of expression of simple (GlcCer, LacCer) and globo-series GSL (Gb3, Gb4) were found for each tumor type. In addition, pre-B ALL expressed the neo-lacto series GSL, paragloboside, which was not significantly seen at later stages of maturation. As a group, leukemias expressed about 10 times higher ratios of simple GSL to Globo-series GSL as compared to lymphomas, regardless of stage of differentiation. Significant amounts of GSL of other series were not found except in one CLL which contained asialo-GM2. GSL phenotype in these cells was not grossly affected by cell genotype since pre-B ALL containing Philadelphia chromosome t(9q;22q) translocations were similar to other ALL; and DHL with t(8q;14q) translocations had GSL patterns similar to other DHL samples and dissimilar to GSL patterns found in Burkitt's lymphomas with t(8q;14q). Differences in GSL expression among the different types of B-cell neoplasm suggested that GSL patterns form a phenotypic map that may complement the traditional glycoprotein immunophenotypic map and contribute to our understanding of the biology of these diseases and B-cell differentiation.     

Differential diagnosis of chronic lymphocytic leukemia/small lymphocytic lymphoma and other indolent lymphomas,including mantle cell lymphoma

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) accounts for approximately 1% of all lymphomas in our department. In this article, we describe the differential diagnosis of CLL/SLL from other indolent lymphomas, with special reference to follicular lymphoma, marginal zone B-cell lymphoma, lymphoplasmacytic lymphoma, and mantle cell lymphoma, although the latter is considered to be aggressive. CLL/SLL often exhibits proliferation centers, similar to follicular lymphoma. Immunohistological examination can easily distinguish these two lymphomas. The most important characteristic of CLL/SLL is CD5 and CD23 positivity. Mantle cell lymphoma is also CD5-positive and there are some CD23-positive cases. Such cases should be carefully distinguished from CLL/SLL. Some marginal zone lymphomas are also positive for CD5 and such cases are often disseminated. Lymphoplasmacytic lymphoma should also be a differential diagnosis for CLL/SLL. It frequently demonstrates MYD88 L265P, which is a key differential finding. By immunohistological examination, the expression of lymphoid enhancer-binding factor 1 is specific for CLL/SLL and can be a good marker in the differential diagnosis.     

Toll-like receptor agonists in the treatment of chronic lymphocytic leukemia.

Advances in our understanding of the Toll-like receptors (TLRs) have led to the identification of several agonists that are suitable for clinical development. Chronic lymphocytic leukemia (CLL) may be especially amenable to TLR agonists because it is an immunologically susceptible tumor with strong expression of several TLRs, particularly TLR-7 and TLR-9. TLR agonists may indirectly clear CLL cells by enhancing the activity of natural killer and tumor-reactive T cells, or by altering the tumor microenvironment and inhibiting angiogenesis. However, signaling pathways can be activated directly in CLL cells by TLR-7 and TLR-9 agonists, leading to the production of cytokines and costimulatory molecules in a manner that is dependent on the underlying cytogenetic abnormalities, but rendering the tumor cells more sensitive to killing by cytotoxic T cells, immunotoxins and some chemotherapeutic drugs. Imidazoquinolines are TLR-7 agonists with strong local activity against CLL, and phase I trials of systemically administered imidazoquinolines (and also cytosine-phosphate-guanosine oligonucleotides that are TLR-9 agonists) are currently ongoing at different centers. The potential importance of these TLR agonists in the treatment of CLL is suggested by their ability to sensitize tumor cells to cytotoxic agents, and their future probably lies in combination with radiotherapies, chemotherapies, monoclonal antibodies and cancer vaccines.     

Rituximab in Lymphoma and Chronic Lymphocytic Leukaemia: A Practice Guideline

Rituximab is the first monoclonal antibody to be approved for use by the US Food and Drug Administration in cancer. Its role in the treatment of non-Hodgkin lymphoma, including chronic lymphocytic leukaemia (CLL), has evolved significantly. We aimed to systematically review and update the literature on rituximab in lymphoma and CLL, and provide evidence-based consensus guidelines for its rational use. Validated methodology from the Cancer Care Ontario Program in Evidence-based Care was used. A comprehensive literature search was completed by a methodologist from the Hematology Disease Site Group of Cancer Care Ontario. Data were extracted from randomised controlled trials of rituximab-containing chemotherapy regimens for patients with lymphoma or CLL. Fifty-six primary randomised controlled trials were retrievable and met all inclusion criteria. Clinically important benefits in progression-free survival or overall survival were seen in the following settings: (i) addition of rituximab to combination chemotherapy for initial treatment of aggressive B-cell lymphomas, including diffuse large B-cell lymphoma, Burkitt lymphoma and HIV-related lymphoma with CD4 count ≥50/mm³; (ii) addition of rituximab to combination chemotherapy for initial and subsequent treatment of follicular lymphoma and other indolent B-cell lymphomas; (iii) use of rituximab maintenance in patients with indolent B-cell lymphomas who have responded to chemoimmunotherapy; (iv) addition of rituximab to fludarabine-based chemotherapy or chlorambucil for initial treatment of CLL. The consensus opinion of the Hematology Disease Site Group is that rituximab is recommended for these indications.     

CD45 expression in low-grade B-cell non-Hodgkin's lymphomas

CD45 is a glycoprotein expressed in all lymphohemopoietic cells. Its expression increases during B-lymphocyte ontogeny. Few data are available about CD45 expression in the various types of low-grade B-cell non-Hodgkin's lymphomas (NHL). Low levels of CD45 have been reported in pathologic lymphocytes from typical chronic lymphocytic leukemia (CLL) and higher levels of this antigen have been observed in some cases of atypical CLL and in some cases of other types of NHL. One hundred and seven bone marrow samples of NHL with bone marrow infiltration were investigated: 45 typical CLL, 15 atypical CLL, 9 mantle cell lymphomas (MCL), 1 MCL with CD23 expression, 18 marginal zone lymphomas (MZL), 6 lymphoplasmacytic lymphomas (LPL), 6 follicular lymphomas (FL), and 7 hairy cell leukemias (HCL). CD45 expression was evaluated by flow cytometry: pathologic lymphocytes were identified on the basis of specific immunophenotypic profile, CD19/K or CD19/lambda co-expression. Results were expressed as median fluorescence intensity (MFI) along a 1024 linear scale. CD45 expression was measured also on autologous T-lymphocytes and a "CD45 index" was calculated as the ratio MFI of pathologic B-lymphocytes/MFI of T-lymphocytes, to normalize the results obtained. We found four CD45 expression patterns: very low in typical CLL; relatively low in MCL; intermediate intensity in MZL, LPL, and FL; very high expression in HCL. Among the atypical cases, very high CD45 expression was found in one case of CD23-negative CLL, in CD23-positive MCL, and CLL with atypical morphology. The results indicate different levels of maturation in low-grade NHL and may help to characterize such neoplasias.     

Triggering of neoplastic B cells via surface IgM and the cell surface antigens CD20 and CDw40. Responses differ from normal blood B cells and are restricted to certain morphologic subsets

By raising monoclonal antibodies (MAbs) against B cells, a number of cell surface molecules have recently been identified which after binding by their specific antibody can trigger B cells, either alone or in co-operation with antibodies to surface immunoglobulin (sIg). The anti-CD20 (Bp35) MAb IF5 can deliver a strong activation signal to resting normal B cells, and the anti-CDw40 (Bp50) MAb G28-5 can promote activated G1 B cells to enter S phase. These antibodies were tested for their functional effects in vitro on suspended cells from 17 follicle-center-cell (FCC) lymphomas, 5 cases of chronic lymphatic B-cell leukemia (B-CLL) and 8 cases of various histological types. Changes in cellular volume, RNA and DNA synthesis were compared with the results obtained with a polyclonal anti-mu [F(ab')2] antiserum, a MAb to surface IgM (AF6), 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and B-cell growth factor (low-molecular-weight BCGF). Our data reveal differences in the requirements for triggering of various B-cell subsets: cells from CLL responded strongly to TPA but not to anti-mu, which is a potent stimulator not only of normal B cells but also of cells from individual cases of FCC lymphomas. Our observations suggest that the differentiation stage of B-CLL cells is distinct from that of small resting B cells from peripheral blood. Centrocytic lymphomas could not be activated by any of the reagents. CD20-mediated triggering was seen in neoplastic B cells from only 4 of 30 cases, indicating that most B-cell neoplasias were not responsive to this activation pathway. In contrast, the anti-CDw40 MAb consistently stimulated DNA synthesis together with anti-mu or TPA in cells from FCC lymphomas, but not from CLL. Together, these results suggest that activation in different neoplastic B-cell subsets depends on distinct signal transduction mechanisms.     

Histological and immunophenotypic changes in 59 cases of B-cell non-Hodgkin's lymphoma after rituximab therapy

Rituximab is a chimeric monoclonal antibody that recognizes the CD20 antigen. It has been used to treat B-cell non-Hodgkin lymphoma (B-NHL), but recently rituximab resistance has been a cause for concern. We examined histological and immunohistochemical changes in 59 patients with B-NHL after rituximab therapy. The patients comprised 32 men and 27 women with a median age of 59 years. Pre-rituximab specimens comprised 34 follicular lymphomas (FL), 11 diffuse large B-cell lymphomas (DLBCL), 10 mantle cell lymphomas, two marginal zone B-cell lymphomas (MZBCL), and two chronic lymphocytic leukemias (CLL). CD20 expression in lymphoma cells was evaluated by immunohistochemistry or flow cytometry. Post-rituximab materials were taken a median of 6 months (4 days to 59 months) after rituximab therapy. Sixteen cases (27%) showed loss of CD20 expression with four histological patterns: pattern 1, no remarkable histological change (FL, 5; DLBCL, 3; and CLL, 2); pattern 2, proliferation of plasmacytoid cells (FL, 2; DLBCL, 1; and MZBCL, 1); pattern 3, transformation to classical Hodgkin's lymphoma (FL, 1); and pattern 4, transformation to anaplastic large cell lymphoma-like undifferentiated lymphoma (FL, 1). Loss of CD20 was unrelated to the interval of biopsies, treatment regimen, clinical response, and frequency of rituximab administration. Loss of CD20 within 1 month of rituximab therapy (3/14, 21%) and regain of CD20 (2/7, 29%) were not frequent. CD20-positive relapse with transformation occurred most frequently in cases of early relapse. In conclusion, B-NHL showed various histological and immunophenotypic changes after rituximab therapy, including not only CD20 loss but also proliferation of plasmacytoid cells or transformation to special subtypes of lymphoma. ( Cancer Sci 2009; 100: 54–61)     

Differential diagnosis of malignant lymphomas and related disorders by specific pattern of expression of immunophenotypic markers revealed by multiparameter flow cytometry (Review)

The introduction of monoclonal antibodies (mAbs) for cell immunophenotyping and use of flow cytometry with the progressively improving software for multivariate analyses have revolutionized the diagnosis and influenced the classification of hematologic neoplasms. In this review we focus on the practical application of flow cytometry in the diagnosis and classification of malignant lymphomas and related lymphoproliferative disorders with special emphasis on differential diagnosis. A general approach to the utilization of flow cytometry (FC) in hematopathology with an algorithm to diagnose the most common neoplasms is presented. We discuss precursor B-cell neoplasms, mature B-cell neoplasms (SLL/CLL, mantle cell lymphoma, marginal zone lymphoma, hairy cell leukemia, diffuse large B-cell lymphoma, plasma cell dyscrasias and lymphomas with plasmacytic differentiation), precursor T-lymphoblastic leukemia and mature (peripheral) T-cell neoplasms, including T-SLL/PLL, anaplastic cell lymphomas and large granular cell leukemia/lymphoma. The text is accompanied by characteristic FC scatterplots of the discussed entities.     

V(H)3-21 gene usage in chronic lymphocytic leukemia--characterization of a new subgroup with distinct molecular features and poor survival

During recent years it has become evident that lymphoproliferative diseases of B-cell origin display preferential immunoglobulin (Ig) variable heavy chain (V_H) gene usage. For instance, the V_H1-69 and V_H4-34 genes were early found to be overexpressed in B-cell chronic lymphocytic leukemia (CLL) and other B-cell lymphomas. The implications of biased V_H gene usage have been speculated to be a result of stimulation of unknown antigens, which gives increased proliferation of B-cells with certain V_H gene configuration and consequently higher probability to undergo transformation. Thus, V_H gene usage may play a role in development of leukemias and lymphomas. Recently, we could confirm the over usage of the V_H1-69 and V_H4-34 genes in CLL, but a novel finding was that the V_H3-21 gene was preferentially utilized in CLL patients with mutated V_H genes. These V_H3-21⁺ Ig rearrangements showed molecular peculiarities such as shorter lengths of the third complementarity determining region (CDR) and had similar amino acid composition of their CDR3s, implicating recognition of the same antigen in individual tumors. Most of the V_H3-21⁺ patients also showed a predominance of λ chain expression and biased usage of 1 specific V_λ gene, V2-14. Furthermore, overall survival appeared to correlate with V_H3-21 usage and, regardless of V_H gene mutation status, V_H3-21⁺ patients had a poor outcome. All in all, it appears that V_H3-21 gene usage define a new entity of CLL. The remaining question now to be clarified is if antigen(s) actually are involved in the pathogenesis of V_H3-21⁺ CLL.     

Expression of DNA mismatch repair proteins in transformed non-Hodgkin's lymphoma: relationship to smoking

It has been hypothesized that defects in DNA-mismatch repair are associated with smoking in certain types of transformed non-Hodgkin lymphoma (NHL). We have analyzed biopsy samples from two indolent B-cell lymphomas, follicular lymphoma (FL) and chronic lymphocytic leukemia/small lymphocytic leukemia (CLL/SLL), that have transformed to diffuse-large B-cell lymphoma (DLBCL). We correlated the presence or absence of DNA-mismatch repair enzymes by immunostaining as well as the p53 status to smoking history. Of all patients (n = 30), 37% showed negative immunostaining of MLH1, 16% showed negative immunostaining of MSH2 and 63% had p53 mutations and/or protein expression. Eighteen out of 20 transformed follicular lymphomas and seven out of 10 CLL/SLL that have transformed to DLBCL (Richter's syndrome) were informative for smoking histories. We found that the relative risk of negative immunostaining for either MLH1 or MSH2 was 2.2 times higher in smokers than non-smokers (relative risk = 2.2041, 95% confidence interval: 0.89714, 5.41491). No direct correlation was found between smoking and the mutations in the p53 gene. These results suggest that cigarette smoking may play a role in the development of transformed lymphomas through defective mismatch repair.     

Clinical outcome of incidental pelvic node malignant B-cell lymphomas discovered at the time of radical prostatectomy

Incidental pelvic node malignant B-cell lymphomas diagnosed at the time of radical prostatectomy are rare. Their clinical outcome has not been studied. We studied thirteen such cases with long-term clinical follow-up. Patients were followed between 9 and 94 months after surgery. Of 13 cases, 9 were chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), 3 marginal zone B-cell lymphoma (MZL) and 1 mantle cell lymphoma (MCL). All 13 patients did not receive radiation or chemotherapy; and five of 13 cases showed hematologic evidence of lymphoma progression between 1 and 5 months after radical prostatectomy. After progression, the mantle cell lymphoma patient received aggressive chemotherapy and had systemic dissemination. Two of 13 cases had recurrent prostate carcinoma. None of 13 patients had died from lymphoma or prostate carcinoma at the last follow-up. In conclusion, most incidental pelvic node lymphomas (8/13) showed no evidence of systemic dissemination to peripheral blood or bone marrow after a mean 42.8 weeks of follow-up despite the fact that no additional treatment was given. Strong consideration should be given to withholding further treatment in patients diagnosed with pelvic low-grade B-cell lymphoma at the time of radical prostatectomy until disease progression occurs.     

The value of the monoclonal antibody, DBA44, in the diagnosis of B-lymphoid disorders

The DBA44 monoclonal antibody described by Al Saati recognizes a membrane antigen expressed by a sub-population of B-lymphocytes. It was tested on paraffin-embedded tissues, and it distinguishes Hairy Cell Leukemia (HCL) from the more common B-cell Chronic Lymphocytic Leukemia (CLL). Neither Splenic Lymphoma with Villous Lymphocytes (SLVL) cases nor Prolymphocytic Leukemia (PLL) cases were tested. We have tested 87 B-lymphoproliferative disorders with DBA44 on cytocentrifuge preparations.All five HCL cases were positive (100%). Of 24 cases of SLVL, 19 were positive (79%); of 58 other B-cell malignancies, five cases were positive (8.5%), including 1/8 CD5-CLLs, 1/5 PLLs and 3/24 lymphomas. All CD5+ CLL were negative.DBA44 positivity cannot distinguish HCL from SLVL, which is the disease that may create major diagnostic problems. In contrast, when we compare SLVL to CLL (which is another diagnostic problem), significant differences were found between the incidence of DBA44 positivity in SLVL and both CD5+ B-CLL (p < 10⁻⁵), and CD5− B-CLL (p < 0.01).The monoclonal antibody DBA44 is positive in HCL and SLVL. It is not helpful in the differential diagnosis of HCL and SLVL. In contrast, when a diagnostic problem arises between SLVL and CLL, the reactivity of DBA44 is of great value.     

Role of CD20 Monoclonal Antibodies in Previously Untreated Chronic Lymphocytic Leukemia

Monoclonal antibodies (MoAbs) directed against the CD20 antigen on B cells have dramatically altered the treatment landscape for patients with chronic lymphocytic leukemia (CLL). Rituximab, a chimeric mouse/human MoAb, was the first antibody to be approved for the treatment of indolent B-cell lymphomas. Although single-agent, standard-dose rituximab has limited activity as first-line therapy for patients with CLL, it has synergistic therapeutic activity when combined with chemotherapy. Indeed, chemoimmunotherapy with combined fludarabine (F), cyclophosphamide (C), and rituximab was shown to improve both progression-free and overall survival in a randomized phase III clinical trial compared with FC in previously untreated patients with CLL. In this article, we review important clinical trials that have incorporated rituximab with other agents for treatment-naive patients with CLL. We also highlight second- and third-generation CD20 MoAbs approved or in development for the treatment of CLL.     

Bendamustine/Mitoxantrone/Rituximab (BMR): a very effective, well tolerated outpatient chemoimmunotherapy for relapsed and refractory CD20-positive indolent malignancies. Final results of a pilot study

We have developed a new chemoimmunotherapy for patients with relapsed or refractory CD20-positive indolent lymphomas and CLL by combining the chemotherapeutic agents Bendamustine (B) and Mitoxantrone (M) with the monoclonal antibody Rituximab. Treatment consisted of (B): 90 mg/m² (80 mg/m² in CLL) day 1 + 2, (M): 10 mg/m² day 1 and (R): 375 mg/m² day 8,15,22 and 29. BM was repeated 3 times starting on day 36, thereafter every 4 weeks. The maximal therapy consisted of 1 × BMR followed by 5 × BM. We have treated 54 patients with BMR. Median age was 68 years (36 - 82). Disease distribution was as follows: 21 B-CLL, 1 B-PLL, 8 lymphoplasmacytic, 14 follicular, 2 mantle cell, 2 marginal zone, 6 secondary high grade. Median number of previous treatments was 2 (1 - 7). ORR was 96% with 41% CR and 55% PR. Median time to progression is 17 months in CLL and has not been reached in indolent lymphomas with a median observation time of 27 months (3 - 60 + ). The time to next antilymphoma treatment is prolonged significantly by BMR. No therapy associated death or hospitalization occurred within the study period. BMR is a well tolerated very effective outpatient treatment for relapsed and refractory CD20-positive indolent lymphomas and CLL.     

PI3K signaling pathway in normal B cells and indolent B-cell malignancies

In chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphomas (NHLs), B-cell receptor signaling leads to activation of the phosphatidylinositol 3-kinase (PI3K) pathway. Idelalisib, a PI3Kδ inhibitor was approved in 2014 by the US Food and Drug Administration (FDA) in combination with rituximab for the treatment of patients with CLL for whom single-agent rituximab would be considered appropriate and as a single agent for patients with relapsed small lymphocytic lymphoma (SLL) and relapsed follicular lymphoma (FL). Following its approval, several trials investigating various PI3Kδ inhibitors as single agents or in combination with chemoimmunotherapy or other molecular targeted agents in CLL and indolent NHL (iNHL) have uncovered some severe autoimmune related toxicities. This review discusses and summarizes the biologic basis and the clinical experience of the PI3Kδ inhibitors in indolent B-cell malignancies.     

The major subtypes of human B-cell lymphomas lack mutations in BCL-2 family member BAD

Members of the BCL-2 gene family are well known for their role in the pathogenesis of B-cell lymphomas in humans and in mouse models. A recent report that knockout mice deficient for the proapoptotic BCL-2 family member gene BAD frequently develop B-cell lymphomas prompted us to analyze a large collection of human B-cell lymphomas for inactivating mutations in the BAD gene. All 3 exons of the BAD gene were amplified and directly sequenced. The 81 lymphomas analyzed included 16 cases of B-cell chronic lymphocytic leukemia, 11 mantle-cell lymphomas, 10 follicular lymphomas, 7 MALT lymphomas, 8 Burkitt's lymphoma cell lines, 3 cell lines of multiple myeloma, 15 cases and 4 cell lines of diffuse large B-cell lymphoma and 7 Hodgkin's lymphoma lines. No mutations were found in any of the cases. We conclude that mutations in the BAD gene do not play a role in the pathogenesis of the major subtypes of human B-cell lymphomas.     

abl oncogene expression in non-Hodgkin lymphomas: correlation to histological differentiation and clinical status

Eight reactive lymphatic tissues, 166 cases of non-Hodgkin lymphomas (NHL) and 11 cases of multiple myeloma were investigated for expression of the c-abl protein using the poly-clonal anti-abl antibody 4411 and an indirect peroxidase technique. In selected cases the results were compared to those obtained with a second polyclonal and 2 monoclonal anti-abl antibodies. In 7 cases, Northern blot analysis of abl-mRNA was performed in parallel. In reactive lymphatic tissues, cells positive for the 4411 antibody were confined to the B-cell areas, i.e., to the mantle zone and parts of the germinal center. In NHL, a positive staining of the cell membrane was predominantly detectable in lymphomas putatively originating in the germinal center or mantle zone (in particular in centrocytic NHL), independent of their proliferative activity. Clinically, 7 out of 8 abl-positive cases of chronic lymphocytic leukemia (CLL) had a more aggressive course of disease, whereas "progressive disease" occurred in only 7 out of 19 c-abl antigen-negative cases. When the clinical status of 78 patients with NHL and 11 patients with multiple myeloma was related to c-abl expression, c-abl-positivity was mostly confined to patients in advanced tumor stages [p less than 0.001 (NHL)].     

Flow-cytometry detection of minimal DNA aneuploidy in mature lymphoid leukemias - comparison with metaphase and interphase cytogenetics

The relative DNA content of peripheral blood cells from 79 cases with lymphoid leukemias was analyzed by a dual-parameter flow cytometric analysis. The leukemia samples corresponded to: chronic lymphocytic leukemia (CLL) 40, CLL with more than 10% prolymphocytes (CLL/PL) 12, CLL mixed 9, prolymphocytic leukemia (PLL) 5, and B-cell lymphoma in leukemic phase 13. DNA aneuploidy was found overall in 26 (32.9%) of the cases and these corresponded to: 7 (17.5%) with CLL, 7 (58.3%) with CLL/PL, 4 (44.4%) with CLL mixed, 2 (40%) with PLL and 6 (46.2%) with B-cell lymphoma. There was a good correlation between DNA content and cytogenetics/fluorescent in situ hybridization in all but 2 cases as follows: 6 of 7 cases with diploid DNA had normal karyotype and only one had trisomy 12: 4 of 6 cases with hyperdiploid DNA had trisomy 12, one had tetraploidy and only one had a normal karyotype. Two cases were hypodiploid both by DNA and cytogenetic analysis. Our findings demonstrate a higher incidence of DNA aneuploidy in B-cell lymphoma in leukemic phase, PLL, and atypical CLL in comparison with typical CLL and a good correlation with cytogenetics. We conclude that flow cytometric DNA analysis represents a useful, sensitive, and rapid method to detect and monitor minimal changes of DNA content in leukemic lymphocytes without the need of short-term cultures.