Usefulness of CD79b expression in the diagnosis of B-cell chronic lymphoproliferative disorders

Novel Targets and Advanced Therapies in Diffuse Large B Cell Lymphomas

Since the introduction of rituximab in the late 1990s, significant progress has been made in advancing targeted therapies for B cell lymphomas, improving patients' chance of being cured and clinicians' therapeutic armamentarium. A better understanding of disease biology and pathogenic pathways, coupled with refinements in immunophenotypic and molecular diagnostics, have been instrumental in these achievements. While traditional chemotherapy remains fundamental in most cases, concerns surrounding chemorefractoriness and cumulative toxicities, particularly the depletion of the hemopoietic reserve, underscore the imperative for personalized treatment approaches. Integrating targeted agents, notably monoclonal antibodies, alongside chemotherapy has yielded heightened response rates and prolonged survival. A notable paradigm shift is underway with innovative-targeted therapies replacing cytotoxic drugs, challenging conventional salvage strategies like stem cell transplantation. This review examines the landscape of emerging targets for lymphoma cells and explores innovative therapies for diffuse large B cell lymphoma (DLBCL). From Chimeric Antigen Receptor-T cells to more potent monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, checkpoint inhibitors, and small molecules targeting intracellular pathways, each modality offers promising avenues for therapeutic advancement. This review aims to furnish insights into their potential implications for the future of DLBCL treatment strategies.

LPS-Induced Inflammation Prior to Injury Exacerbates the Development of Post-Traumatic Osteoarthritis in Mice

Osteoarthritis (OA) is a debilitating and painful disease characterized by the progressive loss of articular cartilage. Post-traumatic osteoarthritis (PTOA) is an injury-induced type of OA that persists in an asymptomatic phase for years before it becomes diagnosed in ~50% of injured individuals. Although PTOA is not classified as an inflammatory disease, it has been suggested that inflammation could be a major driver of PTOA development. Here we examined whether a state of systemic inflammation induced by lipopolysaccharide (LPS) administration 5-days before injury would modulate PTOA outcomes. RNA-seq analysis at 1-day post-injury followed by micro-computed tomography (μCT) and histology characterization at 6 weeks post-injury revealed that LPS administration causes more severe PTOA phenotypes. These phenotypes included significantly higher loss of cartilage and subchondral bone volume. Gene expression analysis showed that LPS alone induced a large cohort of inflammatory genes previously shown to be elevated in synovial M1 macrophages of rheumatoid arthritis (RA) patients, suggesting that systemic LPS produces synovitis. This synovitis was sufficient to promote PTOA in MRL/MpJ mice, a strain previously shown to be resistant to PTOA. The synovium of LPS-treated injured joints displayed an increase in cellularity, and immunohistological examination confirmed that this increase was in part attributable to an elevation in type 1 macrophages. LPS induced the expression of Tlr7 and Tlr8 in both injured and uninjured joints, genes known to be elevated in RA. We conclude that inflammation before injury is an important risk factor for the development of PTOA and that correlating patient serum endotoxin levels or their state of systemic inflammation with PTOA progression may help develop new, effective treatments to lower the rate of PTOA in injured individuals. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Consistency of the Moreau CLL score

BACKGROUND

The Moreau score is essential for the diagnosis of B-cell lymphoproliferative disorders (B-LPD).

METHODS

We assessed the consistency of the Moreau score in a series of 138 patients with at least two samples involved by a B-LPD (316 samples) other than germinal center-derived malignancies, hairy cell leukemia, and mantle cell lymphomas. Patients with evidence of two distinct B-LPDs were also excluded.

RESULTS

We found 53 inconsistencies in 44 of 138 (32%) patients. FMC7 was the most inconsistent (18 cases) and CD5 the least (5 cases). CD200 was inconsistent in 6 of 67 (9%) cases. The most important predictive factor for the finding of antigenic inconsistencies was sampling of a different anatomic site. Other factors, including number of samples, time between samples, or cytogenetic group, were not predictive. For the most part, these inconsistencies did not appear to be clinically relevant.

CONCLUSION

Inconsistencies in the Moreau score are common, supporting the importance of integrated laboratory diagnosis. However, the practical implications of these antigenic inconsistencies are probably limited.

Diagnosis of chronic lymphoproliferative disorders by flow cytometry using four-color combinations for immunophenotyping: A proposal of the brazilian group of flow cytometry (GBCFLUX)

BACKGROUND

Multiparametric flow cytometry (MFC) is a powerful tool for the diagnosis of hematological malignancies and has been useful for the classification of chronic lymphoproliferative disorders (CLPD) according to the WHO criteria. Following the purposes of the Brazilian Group of Flow Cytometry (GBCFLUX), the aim of this report was to standardize the minimum requirements to achieve an accurate diagnosis in CLPDs, considering the different economic possibilities of the laboratories in our country. Most laboratories in Brazil work with 4-fluorescence flow cytometers, which is why the GBCFLUX CLPD Committee has proposed 4-color monoclonal antibody (MoAb) panels.

METHODS/RESULTS

Panels for screening and diagnosis in B, T and NK lymphoproliferative disorders were developed based on the normal differentiation pathways of these cells and the most frequent phenotypic aberrations. Important markers for prognosis and for minimal residual disease (MRD) evaluation were also included. The MoAb panels presented here were designed based on the diagnostic expertise of the participating laboratories and an extensive literature review.

CONCLUSION

The 4-color panels presented to aid in the diagnosis of lymphoproliferative neoplasms by GBCFLUX aim to provide clinical laboratories with a systematic, step-wise, cost-effective, and reproducible approach to obtain an accurate immunophenotypic diagnosis of the most frequent of these disorders. © 2016 International Clinical Cytometry Society.

Possible role of CD22, CD79b and CD20 expression in distinguishing small lymphocytic lymphoma from chronic lymphocytic leukemia

Aim of the study

Flow cytometry has an important role in diagnosis and classification of B-cell lymphoproliferative disorders (BCLPDs). However, in distinguishing chronic lymphocytic leukemia (CLL) from small lymphocytic lymphoma (SLL) only clinical criteria are available so far. Aim of the study was to determine differences in the expression of common B cell markers (CD22, CD79b and CD20) on the malignant lymphocytes in the peripheral blood samples of CLL and SLL patients.

Material and methods

Peripheral blood samples of 56 CLL and 11 SLL patients were analyzed by 5-color flow cytometry on the CD45/CD19/CD5 gate for CD22, CD79b and CD20.

Results

In the samples collected from the CLL patients, CD22 expression was detected in only 20% of patients in the low pattern, while in SLL patients the expression was medium and present in 90.9% of patients (p < 0.0001). For CD79b expression, statistical significance is reached both in the expression pattern, which was low/medium for CLL and high for SLL, and expression level (p = 0.006). The expression of CD20 was counted as the CD20/CD19 ratio. The average ratio was 0.512 in the CLL patients vs. 0.931 in the SLL patients (p = 0.0001).

Conclusions

The pattern of expression and expression level of CD22, CD79b and CD20 in peripheral blood could be used for distinguishing SLL from CLL patients.

Pathologic and molecular genetic features of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is an indolent B-cell leukemia. While many patients may not require therapy, some patients will suffer a progressive course and die of their disease. This clinical heterogeneity is reflected in the molecular genetic heterogeneity that is becoming apparent through studies of immunoglobulin heavy chain gene mutational status, chromosomal numerical abnormalities, microRNA abnormalities, and genetic abnormalities identified by whole genome sequencing. Indeed, many of these studies are becoming routine in the assessment of patients with CLL or being incorporated into clinical trials to further stratify patients for appropriate therapies. Here, we will review the morphologic, immunophenotypic, and molecular genetic features of CLL and touch upon the concept of monoclonal B-cell lymphocytosis.

Synopsis and synthesis of candidate-gene association studies in chronic lymphocytic leukemia: the CUMAGAS-CLL information system

A comprehensive and systematic assessment of the current status of candidate-gene association studies for chronic lymphocytic leukemia (CLL) was conducted. Data from 989 candidate-gene association studies (1992-2009) involving 905 distinct genetic variants were analyzed and cataloged in CUMAGAS-CLL, a Web-based information system which allows the retrieval and synthesis of data from candidate-gene association studies on CLL (http://biomath.med.uth.gr). Nine genetic variants (BAX (rs4645878), GSTM1 (null/present), GSTT1 (null/present), IL10 (rs1800896), LTA (rs909253), MTHFR (rs1801131), MTHFR (rs1801133), P2RX7 (rs3751143), and TNF (rs1800629)) were investigated in 4 or more studies, and their results were meta-analyzed. In individual studies, 147 variants showed a significant association with CLL risk under any genetic model. For 53 variants, the association was significant at P < 0.01 with an increased risk greater than 40%. Only 0.3% of studies had statistical power greater than 80%. In meta-analyses, none of the variants showed significant results, and heterogeneity ranged from none to high. Large and rigorous genetic studies (candidate-gene association studies and genome-wide association studies) designed to investigate epistatic and gene-environment interactions may produce more conclusive evidence about the genetic etiology of CLL. CUMAGAS-CLL would be a useful tool for current genomic epidemiology research in the field of CLL.

The leukemias of mature lymphocytes

The leukemias of mature B cells and T cells are a limited set of diseases in which blood and bone marrow are the primary sites of involvement. Although they may superficially resemble one another, they have distinct clinical and pathologic features and must be distinguished from one another. In this article, the major clinical, morphologic, phenotypic, and molecular genetic features of the mature B- and T-cell leukemias are reviewed, and differential diagnostic considerations are discussed.

Predictive value of blood and bone marrow flow cytometry in B-cell lymphoma classification: comparative analysis of flow cytometry and tissue biopsy in 252 patients

OBJECTIVE

To study the effectiveness of peripheral blood (PB) and bone marrow flow cytometric immunophenotyping (FCIP) in predicting the histologic B-cell lymphoma type.

PATIENTS AND METHODS

We studied the FCIP results and tissue histopathology from 252 patients with B-cell lymphoma seen at Mayo Clinic's site in Rochester, MN, between January 1, 1997, and January 1, 2004, who had positive results on PB, bone marrow, or body fluid FCIP and a corresponding diagnostic tissue biopsy specimen.

RESULTS

Most of the B-cell lymphomas studied were low grade, with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma being most common. Flow cytometric immunophenotyping histogram analysis was more informative than tabulated percentage antigen positivity; surface immunoglobulin and CD20 staining intensity, CD5 and CD23 positivity, CD10 positivity, and the coexpression of CD11c/CD22 and CD103 were the most pertinent markers. Using these FCIP parameters and strict immunophenotypic definitions for CLL, mantle cell lymphoma (MCL), and hairy cell leukemia, we obtained greater than 95% specificity for each diagnosis. However, we encountered the following exceptions to standard paradigms of B-cell lymphoma-associated FCIP: (1) CD5 expression by disorders distinct from CLL and MCL, (2) lack of uniform CD5 positivity in some CLL and MCL cases, (3) absence of CD10 in approximately 50% of follicular lymphomas, and (4) expression of CD103 by occasional marginal zone lymphomas.

CONCLUSION

Stringent interpretation of PB and bone marrow FCIP results enables identification of certain B-cell lymphoma types. However, the observed exceptions to accepted immunophenotypic paradigms highlight the occasional phenotypic overlap among diseases and emphasize that a systematic approach to FCIP interpretations is key to providing clinically useful diagnostic information.

Pathology of chronic lymphocytic leukemia: an update

Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) is a clonal lymphoproliferative disorder characterized by proliferation of morphologically and immunophenotypically mature lymphocytes. CLL/SLL may proceed through different phases: an early phase in which tumor cells are predominantly small in size, with a low proliferation rate and prolonged cell survival, and a transformation phase with the frequent occurrence of extramedullary proliferation and an increase in large, immature cells. Although some patients with CLL have an indolent disease course and die after many years of unrelated causes, others have very rapidly disease progression and die of the disease within a few years of the diagnosis. In the past few years, considerable progress has been made in our ability to diagnose and classify CLL accurately. Through cytogenetics and molecular biology, it has been shown that CLL and variants are associated with a unique genotypic profile and that these genetic lesions often have a direct bearing on the pathogenesis and prognosis of the disease. Similarly, the development of antibodies to new biologic markers has allowed the identification of a unique immunophenotypic profile for CLL and variants. Moreover, accumulating evidence suggests that CLL cells respond to selected microenvironmental signals and that this confers a growth advantage and an extended survival to CLL cells. In this article, we will review the progress in the pathobiology of CLL and give an update on prognostic markers and tools in current pathology practice for risk stratification of CLL.

Applications of Flow Cytometry and Immunohistochemistry to Diagnostic Hematopathology

Objective.—Diagnostic hematopathology depends on the applications of flow cytometric immunophenotyping and immunohistochemical immunophenotyping combined with the cytomorphology and histologic features of each case. Select cases may require additional ancillary cytogenetic and molecular studies for diagnosis. The purpose of this review is to focus on the applications of flow cytometric and immunohistochemical immunophenotyping of paraffin-embedded tissue to diagnostic hematopathology. Advantages and disadvantages of these techniques are examined.

Data Sources.—The literature is extensively reviewed (PubMed 1985–2003) with an emphasis on the most recent applications and those that are most useful clinically, both diagnostically and prognostically.

Study Selection.—Studies were selected based on statistically significant results in large studies with reported adequate clinical follow-up.

Data Extraction.—The methodology was reviewed in the selected studies to ensure reliable comparison of reported data.

Data Synthesis.—Flow cytometric immunophenotyping offers the sensitive detection of antigens for which antibodies may not be available for paraffin immunohistochemical immunophenotyping. However, paraffin immunohistochemical immunophenotyping offers preservation of architecture and evaluation of expression of some proteins, which may not be available by flow cytometric immunophenotyping. These techniques should be used as complimentary tools in diagnostic hematopathology.

Conclusions.—There are extensive applications of flow cytometric and immunohistochemical immunophenotyping to diagnostic hematopathology. As cytogenetic and molecular findings evolve in diagnostic hematopathology, there may be additional applications of flow cytometric and immunohistochemical immunophenotyping to this field of pathology.

Pan B-cell markers are not redundant in analysis of chronic lymphocytic leukemia (CLL)

BACKGROUND

The classic immunophenotype for chronic lymphocytic leukemia (CLL) is CD19(+), restricted dim surface expression of kappa or lambda light chain, CD5(+), CD23(+), dim CD20(+), negative FMC7, and negative CD79b. However, the necessity of assaying for all 3 pan B-cell markers (CD20, FMC7, and CD79b) by flow cytometry has not been definitively documented for CLL.

METHODS

Qualitative patterns and semi-quantitative assessment of staining intensity for CD20, FMC7 and CD79b were performed in 70 cases with a current or prior diagnosis of CLL or CLL with increased prolymphocytes leukemia (CLL/PL). The concurrent morphology in 66 of 70 specimens was classified as typical CLL in 53 cases, CLL/PL in 10 cases, and large cell lymphoma in 3 cases.

RESULTS

Forty percent of the cases varied from the characteristic immunophenotype by having moderate or bright staining of CD20 (36%), FMC7 (7%), and/or CD79b (18%). Discrepant qualitative staining patterns were found between FMC7 and CD20 (21%), CD20 and CD79b (15%), and CD79b and FMC7 (10%). Semiquantitative measurement of staining intensity showed little correlation between CD79b and CD20 or FMC7. Moderate correlation was seen between CD20 and FMC7. No correlation was observed between morphology and intensity of marker expression.

CONCLUSIONS

Variable patterns and intensity of staining were seen for FMC7, CD20, and CD79b in this cohort of CLL samples. Dim or negative staining was most consistently seen for FMC7 (93% of specimens). Although FMC7 staining intensity was moderately correlated with CD20, CD79b intensity was poorly correlated with either CD20 or FMC7, and thus, may provide some independent information.

CD79b expression in chronic lymphocytic leukemia. Association with trisomy 12 and atypical immunophenotype

CONTEXT

CD79b is a relatively newly characterized B-cell marker that is expressed in a minority of chronic lymphocytic leukemia (CLL) cases.

OBJECTIVE

To systematically correlate CD79b expression with specific morphologic and immunophenotypic findings and trisomy 12.

DESIGN

We assessed CD79b expression in 100 consecutively accrued CLL cases that were also analyzed by conventional cytogenetics. Based on the association between trisomy 12 and CD79b expression, we then assessed 43 additional CLL cases with trisomy 12. CD79b expression was correlated with morphology and expression of other immunophenotypic markers.

RESULTS

Eighteen (18%) of 100 consecutively accrued cases were CD79b positive. No significant association was found between CD79b expression and atypical morphology. CD79b expression correlated with CD22 and FMC7 positivity. Eight (8%) cases had trisomy 12; 4 (50%) of these were CD79b positive, suggesting an association with trisomy 12. Examination of a second group of 51 CLL cases with trisomy 12 (including 8 cases from the initial study group) showed that CD79b was positive in 26 cases (49%), a frequency significantly higher than that of the consecutively accrued CLL cases without trisomy 12 (P <.05).

CONCLUSIONS

We conclude that CD79b immunoreactivity is positive in approximately 20% of CLL cases and that expression correlates with trisomy 12 and atypical immunophenotypic findings.

Prognostic significance of CD38 and CD20 expression as assessed by quantitative flow cytometry in chronic lymphocytic leukaemia

CD38 expression on chronic lymphocytic leukaemia (CLL) cells is a poor prognostic factor, however, methods for measuring this vary. The QuantiBRITETM flow cytometry (FC) system yields an absolute antigen expression value (antibodies bound/cell, ABC) and may be useful in standardizing CD38 expression analysis. We evaluated cryopreserved pretreatment CLL cells for CD20 ABC, CD38 ABC, and percentage of CD38+ B cells from 131 patients requiring therapy. The 92 patients (70%) with >/= 100 CD38 ABC had worse overall survival (OS; 34% at 5 years) compared with those with < 100 CD38 ABC (70% at 5 years, mortality hazard ratio 2.30, 95% confidence interval 1.28-4.12; two-tailed P = 0.003). Among the 64 patients with < 30% CD38+ cells, OS of the 25 with >/= 100 ABC was worse than that of the 39 with < 100 ABC (P = 0.018). OS of patients with < 30% CD38+ cells and >/= 100 ABC was actually similar to that of patients with >/= 30% CD38+ cells. BrightCD20 expression (>/= 20 000 ABC) was not associated with a worse OS (P = 0.10). The presence of >/= 100 CD38 ABC in CLL patients requiring therapy is an unfavourable prognostic factor for OS and quantitative FC may be superior to percentage CD38+ cell assessment. Prospective trials are required to determine more precisely the prognostic significance of absolute expression levels in fresh CLL cells.

Guess what: Chronic 13q14.3+/CD5-/CD23+ lymphocytic leukemia in blood and t(11;14)(q13;q32)+/CD5+/CD23- mantle cell lymphoma in lymph nodes!

We report a case of a patient with two B-cell lymphoproliferative disorders: CD5(-)/CD23(+) B-cell chronic lymphocytic leukemia and CD5(+)/CD23(-) mantle cell lymphoma. These disorders were diagnosed simultaneously based on flow cytometry, immunohistochemistry, fluorescence in situ hybridization, and polymerase chain reaction-based molecular studies. The B-cell lymphocytic leukemia clone predominated in the blood and bone marrow, whereas the mantle cell clone predominated in lymph nodes.

Primary cutaneous lymphoblastic lymphoma presenting in an 8-week old infant

BACKGROUND

We report a case of primary cutaneous lymphoblastic lymphoma (LBL) presenting in an 8-week-old infant.

METHODS

Histopathology and flow cytometric analysis confirmed the diagnosis of a lymphoblastic lymphoma. The cells expressed CD19, CD20, CD34 and surface immunoglobulin (sIg).

RESULTS

The cells were negative for TdT and CD99. This unusual immunophenotype has been described as "transitional pre-B-cell", in that the cells express both immature markers (CD34) and mature markers (sIg).

CONCLUSIONS

To our knowledge, only five other cases of sIg positive precursor B-cell LBL have been reported in the literature. This may represent the youngest reported case of primary cutaneous LBL, occurring at 8weeks of age.

Properties of the mantle cell and mantle cell lymphoma

The major lymphoid inhabitant of the follicular mantle is the mantle cell, an immunologically naïve B cell. It is the putative cell of origin of mantle cell lymphoma (MCL), the cells of which have similar morphologic, immunophenotypic, and molecular characteristics to the normal B lymphocytes of the mantle zone. In the past year a number of advances have been made in the biology of the normal mantle cell, its interactions with the other constituents of the follicular and mantle zone microenvironments, and the development of neoplasia in this cell population. In addition, new developments in diagnostic molecular pathology have been used to more readily identify cases of MCL. The authors summarize these new advances in the understanding of the biology of the mantle cell and newer ancillary techniques in the diagnosis of lymphomas arising from this cell type.

Use of novel t(11;14) and t(14;18) dual-fusion fluorescence in situ hybridization probes in the differential diagnosis of lymphomas of small lymphocytes

Increasingly, molecular biologic techniques have become important in the diagnosis of non-Hodgkin lymphomas. In the differential diagnosis of lymphoma(s) of small lymphocytes (LSL), reliable detection of t(11;14) or t(14;18) would confirm the diagnosis of mantle cell lymphoma (MCL) or follicle center lymphoma (FCL), respectively. A total of 87 LSL cases (27 MCL, 39 FCL, 17 small lymphocytic lymphoma [SLL], 3 marginal zone lymphomas, and 1 paraimmunoblastic variant of SLL) were diagnosed by a combination of light microscopy, immunohistochemistry, and flow cytometric immunophenotyping. Interphase fluorescence in situ hybridization (FISH) for t(11;14) and t( 14;18) using dual-fusion probes (Vysis, Downers Grove, IL) was performed on touch (n = 69) or gravity (n = 18) preparations from these cases. Of 27 MCL cases tested, 25 (93%) had demonstrable t(11;14), none had t(14;18), and 2 were negative for t(11;14) and t(14;18). Twenty-five of 39 (64%) FCL cases had t(14;18), none had t(11;14), and the remaining FCL cases (14 cases [35%]) had neither t(11;14) nor t(14;18). All 17 (100%) SLL cases had neither t(11;14) nor t(14;18). All 3 (100%) marginal zone lymphoma cases had neither t(11;14) nor t(14;18). The case of paraimmunoblastic variant of SLL had t(11;14) and was negative for t(14;18). No discrepant [i.e., positive for both t(11;14) and t(14;18)] or false-positive cases were noted. Interphase FISH using these commercially available probes is a useful adjunct to light microscopy, immunohistochemistry, and flow cytometric immunophenotyping in the diagnosis of LSL. FISH can be performed successfully on archival single-cell preparations (touch preparations or gravity preparations) when fresh tissue is unavailable. No discordant or false-positive cases were identified.

Typical and atypical chronic lymphocytic leukemia differ clinically and immunophenotypically

We compared the features of 17 cases of atypical chronic lymphocytic leukemia (aCLL) with those of a clinical control group of 24 cases of CLL. Quantitative flow cytometric data, available for 12 cases, were compared with an immunophenotypic control group of 58 cases using a relative fluorescence indexfor CD5, CD23, CD79b, and surface immunoglobulin light chain (sIg). Compared with the clinical control group, patients with aCLL had a higher mean WBC count and a lower platelet count. Patients with aCLL had a significantly higher probability of disease progression. Compared with an immunophenotypic control group of 58 CLL cases, 12 cases of aCLL demonstrated significantly higher expression of CD23. There was no significant difference in expression of sIg, CD79b, or CD5 between the groups. CD38 expression was noted in only 1 (9%) of 11 tested cases; 2 (18%) of 11 cases had trisomy 12. aCLL can be distinguished from typical CLL morphologically, clinically, and immunophenotypically. Atypical morphologic features in CLL seem to be a marker of aggressive clinical behavior.

Atypical lymphocytic leukemia and mantle cell lymphoma immunologically very close: flow cytometric distinction by the use of CD20 and CD54 expression

Integration of morphological and immunophenotypic data is critical in achieving diagnosis accuracy and minimising interobserver interpretative discrepancies. The aim of this work was to compare the immunophenotype and the morphology of chronic lymphocytic leukaemia and mantle cell lymphoma, to help in the differential diagnosis of CD5 positive monoclonal B cells. Frozen/thawed samples from 91 patients were analysed retrospectively. Fresh samples from 17 mixed/atypical CLL and 13 MCL were tested to corroborate the results. Markers were analysed as percentage (%) of positive B lymphocyte subpopulation, and in terms of median fluorescence intensity (MFI). Matutes's CLL score clearly allowed distinguishing between classical CLL on the one hand, and atypical CLL and MCL on the other hand. The percentage of CD54-positive cells and the median fluorescence intensity of CD20 and CD54 were the only parameters which were significantly higher in MCL than in atypical CLL (P < 0.05), allowing an immunological distinction between these two entities. Nevertheless, due to a quenching problem when using CD20 and CD54 together, and because CD18 showed a statistically different expression between classical and atypical CLL, the combination of CD18/CD54 has been preferred and showed a different pattern in the three entities. Immunophenotyping could be helpful in the differential diagnosis of CD5-positive B cell chronic lymphoproliferative disorders with atypical features that do not fit exactly into any of the morphologic proposed groups.

High resolution immunophenotypic analysis of chronic lymphocytic leukemic cells by enzymatic amplification staining

Immunophenotypic analysis of chronic lymphocytic leukemia (CLL) cells is essential for the diagnosis of this disorder. Unfortunately, surface immunoglobulin light chains and CD79b are expressed faintly or not at all by CLL cells from many patients. We developed an enzymatic amplification staining procedure that amplifies the fluorescent signal by 10- to 100-fold. By using this technology, we have been able to resolve immunoglobulin light chain exclusion and CD79b expression on the cells from most cases. This new capability can be used for high-resolution immunophenotypic analysis of leukemias and lymphomas.

Pathologic diagnosis of mantle cell lymphoma

Mantle cell lymphoma (MCL) is a clinicopathologic entity with distinctive morphologic and immunophenotypic features and a characteristic cytogenetic abnormality, the t(11;14)(q13;q32). Although MCL was recognized over 30 years ago, a lack of consensus regarding its morphologic features precluded its inclusion into non-Hodgkin's lymphoma (NHL) classification schemes until relatively recently. An accurate diagnosis of MCL is of great importance, since this tumor generally carries a poor prognosis and requires more aggressive and novel treatment regimens. In this article, we briefly overview the clinical features of MCL and then focus on the pathologic diagnosis of MCL, emphasizing morphologic findings and various ancillary techniques useful in the diagnostic workup. Involvement of lymph nodes and other sites, such as the spleen, liver, gastrointestinal tract, Waldeyer's ring, bone marrow, peripheral blood, and cerebrospinal fluid are reviewed. The diagnosis of high-grade variants of MCL is a particular challenge, as these tumors exhibit a broad spectrum of morphologic findings that can be misinterpreted as other types of NHL. The molecular basis of MCL is also briefly reviewed to highlight the biologic role of the t(11;14) and cyclin D1 overexpression in this tumor and the value of immunophenotypic and molecular methods for their detection as diagnostic aids.