Lymphocyte immunophenotyping of B-cell lymphomas: a flow cytometric analysis of neoplastic and nonneoplastic cells in 271 cases

Morphology and multiparameter flow cytometry combined for integrated lymphoma diagnosis on small volume samples: possibilities and limitations

The diagnosis of lymphoma relies mainly on clinical examination and laboratory explorations. Among the latter, morphological and immunohistochemical analysis of a tissue biopsy are the cornerstones for proper identification and classification of the disease. In lymphoma with blood and/or bone marrow involvement, multiparameter flow cytometry is useful. This technique can also be applied to fresh cells released from a biopsy sample. For full comprehension of lymphomas, surgical biopsies are best and indeed recommended by the hematopathological community. Currently, however, there is a global trend towards less invasive procedures, resulting in smaller samples such as core needle biopsies or fine needle aspirations which can make the diagnosis quite challenging. In this review, the possibilities and limitations to make an accurate lymphoma diagnosis on such small volume material are presented. After recalling the major steps of lymphoma diagnosis, the respective value of histology, cytology, and flow cytometry is discussed, including handling of small specimens. The benefits of an integrated approach are then evoked, followed by discussion about which attitude to adopt in different contexts. Perhaps contrary to the prevailing view among many pathologists, a full diagnosis on small volume material, combined with relevant ancillary techniques, is often possible and indeed supported by recent literature. A glimpse at future evolutions, notably the merit of artificial intelligence tools, is finally provided. All in all, this document aims at providing pathologists with an overview of diagnostic possibilities in lymphoma patients when confronted with small volume material such as core needle biopsies or fine needle aspirations.

The patterns and diagnostic significance of the lack of surface immunoglobulin light chain on mature B cells in clinical samples for lymphoma workup

BACKGROUND

Surface immunoglobulin (sIg) light chains are not always detected on mature B cells. This may present as a challenge for clonality determination in clinical flow cytometry.

METHODS

To explore the mechanism and diagnostic significance of sIg negative mature B cells, we retrospectively studied 14 cases of sIg negative reactive B-cell lymphocytosis and 89 cases of sIg negative mature B-cell lymphomas. The expression patterns of sIg and cytoplasmic immunoglobulin (cIg) light chains were studied by flow cytometry using both monoclonal and polyclonal antibodies.

RESULTS

These 14 cases of sIg negative reactive B-cell lymphocytosis were proven to be polytypic based on cytoplasmic light chain studies. In 89 cases of sIg negative mature B-cell lymphomas, we described four distinct patterns of abnormal light chain expression including partial or complete loss of sIg or cIg, suggesting different underlying mechanisms.

CONCLUSIONS

This study represents the first reported series of body or cystic fluids where reactive B cells do not have detectable sIg, arguing strongly against making a diagnosis of B-cell lymphoma based on lack of sIg in mature B cells. Since the lack of sIg does not always predict clonal/neoplastic mature B-cell proliferation, further cIg evaluation should be performed when sIg expression is not detected in mature B cells. The lack of both sIg and cIg in mature B cells may serve as a reliable surrogate clonality/neoplastic marker.

Cytologic and Molecular Diagnostics for Vitreoretinal Lymphoma: Current Approaches and Emerging Single-Cell Analyses

Vitreoretinal lymphoma (VRL) is a rare ocular malignancy that manifests as diffuse large B-cell lymphoma. Early and accurate diagnosis is essential to prevent mistreatment and to reduce the high morbidity and mortality associated with VRL. The disease can be diagnosed using various methods, including cytology, immunohistochemistry, cytokine analysis, flow cytometry, and molecular analysis of bulk vitreous aspirates. Despite these options, VRL diagnosis remains challenging, as samples are often confounded by low cellularity, the presence of debris and non-target immunoreactive cells, and poor cytological preservation. As such, VRL diagnostic accuracy is limited by both false-positive and false-negative outcomes. Missed or inappropriate diagnosis may cause delays in treatment, which can have life-threatening consequences for patients with VRL. In this review, we summarize current knowledge and the diagnostic modalities used for VRL diagnosis. We also highlight several emerging molecular techniques, including high-resolution single cell-based analyses, which may enable more comprehensive and precise VRL diagnoses.

Oligonucleotide Aptamer-Mediated Precision Therapy of Hematological Malignancies

Precision medicine has recently emerged as a promising strategy for cancer therapy because it not only specifically targets cancer cells but it also does not have adverse effects on normal cells. Oligonucleotide aptamers are a class of small molecule ligands that can specifically bind to their targets on cell surfaces with high affinity. Aptamers have great potential in precision cancer therapy due to their unique physical, chemical, and biological properties. Therefore, aptamer technology has been widely investigated for biomedical and clinical applications. This review focuses on the potential applications of aptamer technology as a new tool for precision treatment of hematological malignancies, including leukemia, lymphoma, and multiple myeloma.

Aptamer Internalization via Endocytosis Inducing S-Phase Arrest and Priming Maver-1 Lymphoma Cells for Cytarabine Chemotherapy

The goal of precision therapy is to efficiently treat cancer without side effects. Aptamers are a class of small ligands composed of single-stranded oligonucleotides that bind to their targets with high affinity and specificity. In this study, we identified an ssDNA aptamer specifically targeting Maver-1 lymphoma cells with high binding affinity (Kd = 70±8 pmol/L). Interestingly, cellular cycle studies revealed that exposure of Maver-1 cells to synthetic aptamers triggered S-phase arrest of 40% of the cells (vs. 18% baseline). Confocal microscopy confirmed specific cell binding of aptamers and the resultant endocytosis into Maver-1 cells. Subsequent functional assays validated the fact that aptamer internalization into targeted cells is a prerequisite for Maver-1 cell growth inhibition. Importantly, aptamer-induced S-phase arrest induced enhanced chemotherapeutic results involving cytarabine, which primarily kills lymphoma cells at S-phase. Combination treatments revealed that aptamer re-exposure considerably primed Maver-1 cells for cytarabine chemotherapy, thus achieving a synergistic killing effect by reaching cell death rates as high as 61% (vs. 13% or 14% induced by aptamer or cytarabine treatment alone). These findings demonstrated that aptamers do not only act as molecular ligands but can also function as biotherapeutic agents by inducing S-phase arrest of lymphoma cells. In addition, logical combination of aptamer and cytarabine treatments ushers the way to a unique approach in precision lymphoma chemotherapy.

Inconclusive flow cytometric surface light chain results; can cytoplasmic light chains, Bcl-2 expression and PCR clonality analysis improve accuracy of cytological diagnoses in B-cell lymphomas?

BACKGROUND

Flow cytometric immunophenotyping (FCI), is widely used in cytology for distinguishing between B-cell lymphoma (BCL) and reactive lymphocytic proliferations (RLP), mainly by identifying monotypic B-cell populations. Since this cannot always be determined by ratios of surface immunoglobulin light chains (sIg LCs) we wanted to assess if cytoplasmic immunoglobulin (cIg) LCs, Bcl-2 and polymerase chain reaction (PCR) based clonality analysis can improve accuracy of cytological diagnoses of BCL.

METHODS

Our study included 98 fine needle aspiration biopsies from lymph nodes suspicious for BCL with inconclusive sIg LCs. In all cases PCR clonality analysis was performed in order to determine immunoglobulin heavy chain (IGH) gene and T-cell receptor (TRC) gene rearrangement. In selected cases expression of Bcl-2 and cIg LC were determined by FC.

RESULTS

Thirty patients had lymphoma and 68 had reactive lymphocytic proliferations. Three patterns of sIg LCs staining were found: negative, dual positive and difficult to interpret. Percentage of lymphomas was highest in the dual positive group (75 %). Morphology coupled with cIg LCs determination and/or Bcl-2 expression was able to give a correct diagnosis in 83 % of cases. Molecular tests would have been misleading in 15 % of cases because 7/30 BCL were polyclonal and 8/68 RLP were monoclonal.

CONCLUSIONS

Determination of cIg LCs, Bcl-2 expression and PCR clonality analysis of B cells improved accuracy of cytological diagnoses in BCL with inconclusive sIg LC. However, clonality determined by PCR was misleading in some cases.

Kappa and lambda light chain mRNA in situ hybridization compared to flow cytometry and immunohistochemistry in B cell lymphomas

Background

Detection of B cell clonality is useful for assisting in the diagnosis of B cell lymphomas. Clonality assessment can be accomplished through evaluation of KAPPA and LAMBDA light chain expression. Currently, only slide based methods are available for the majority of patient biopsies and do not detect light chain protein or mRNA in many B-cell lymphomas. Herein we evaluated a new method, known as colorimetric in situ hybridization (CISH), with improved sensitivity and multiplexing capacity, for its usefulness in clonality detection in mature B cell malignancies.

Methods

The KAPPA and LAMBDA ISH was performed on a Ventana Benchmark XT utilizing two color chromogenetic detection. The probes comprised 2 haptenated riboprobes each approximately 500 base pairs long directed against the conserved regions of either KAPPA or LAMBDA mRNA. The dual colors consisted of silver deposition (black) for KAPPA light chain and a novel (pink) chromogen for LAMBDA light chain. Following optimization, CISH allowed visualization of mRNA in benign B cells in reactive tissues including germinal center, mantle zone, and post-germinal center cells. We then identified 79 cases of B cell lymphoma with formalin-fixed paraffin-embedded (FFPE) biopsies including: follicular (36 cases), mantle cell (6 cases), marginal zone (12 cases), lymphoplasmacytic (6 cases), small lymphocytic (4 cases), and diffuse large B cell (15 cases), which were selected on the basis of either prior flow cytometry or immunohistochemistry (IHC) results to serve as the predicate, "gold standard," comparator.

Results

39/79 (49.4%) cases were classified as KAPPA and 29/79 (36.7%) as LAMBDA light chain restricted; while 9/79 (11.3%) cases were classified as indeterminate. Of the 70 cases with KAPPA or LAMBDA light chain restricted CISH, 69/70 (98.6%) were concordant with the reference method, while 1/70 (1.4%) was discordant.

Conclusions

Optimized CISH detected lower levels of mRNA than can be visualized with current slide based methods, making clonality assessment in FFPE biopsies possible for mature B cell neoplasms. In this preliminary study, CISH was highly accurate compared to flow cytometry or IHC. CISH offers the possibility of wider applicability of light chain ISH and is likely to become a useful diagnostic tool.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1430491067123856

Flow cytometric analysis of surface light chain expression patterns in B-cell lymphomas using monoclonal and polyclonal antibodies

Light chain (LC) expression by flow cytometry (FC) in B cell non-Hodgkin lymphomas (B-NHLs) can occasionally be detected with one anti-LC antibody but not with another. We retrospectively analyzed 564 four-color FC files from B-NHLs, assessing LC staining with monoclonal antibodies (mAbs) and polyclonal antibodies (pAbs). Discrepancies in LC expression between mAbs and pAbs were present in 9.2% of cases, mainly in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; 11.1%), diffuse large B-cell lymphoma (DLBCL; 10.2%), follicular lymphoma (9.5%), and mantle cell lymphoma (11.1%) and most frequently in body fluids. Equal proportions of cases were LC+ only with pAbs (4.8%) or mAbs (4.4%). Negative LC expression with both antibodies was present in 7.5% of cases, most frequently in DLBCL (21.6%) and body fluids (27.6%). Evaluation with both mAbs and pAbs increases the sensitivity for LC detection, with no single reagent outperforming the other, although CLL/SLL preferentially showed LC expression with pAbs.

Immunophenotypic variations of Burkitt lymphoma

Burkitt lymphoma (BL) exhibits a characteristic immunophenotype that is positive for pan-B-cell antigens and CD10 and expresses clonal surface immunoglobulins (SIgs). We evaluated 35 BLs and identified atypical immunophenotypes in 4 including SIg light chain negativity in 4, negativity for B-cell antigens in 2, lack of CD10 in 1, and CD4 expression in 1. All 4 cases showed morphologic features characteristic of BL, and all were confirmed by cytogenetic analysis. The 4 BL cases included 1 girl, 2 men with HIV/AIDS, and a third man with a history of heart transplantation. Two patients died shortly after diagnosis; the other 2 completed hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone with highly active antiretroviral therapy and achieved complete remission. Our study indicates that an unusual immunophenotype is not uncommon in BL. If the immunophenotype is interpreted in isolation, the diagnosis could be missed. Recognizing the variability of immunophenotype is essential for establishing an accurate diagnosis of BL.

Lack of surface immunoglobulin light chain expression by flow cytometric immunophenotyping can help diagnose peripheral B-cell lymphoma

We determined the prevalence and significance of finding B cells without surface immunoglobulin (SIg) light chain expression. The flow cytometry database at Johns Hopkins Medical Institutions was searched for cases in which immunoglobulin light chain staining was performed to rule out a B-cell malignant neoplasm between January 1994 and February 2000. We excluded plasma cell dyscrasias, precursor B-cell acute lymphoblastic leukemia/lymphomas, and hematogones. Cases with more than 25% of B cells lacking SIg light chain expression were retrieved. Polymerase chain reaction assays for immunoglobulin heavy chain gene rearrangements were performed in SIg-negative cases with available tissue blocks. We identified 36 cases; all represented lymphoma. Their diagnoses included diffuse large B-cell lymphoma (20), HIV-related lymphoma (5), follicular lymphoma (5), Burkitt lymphoma (2), monomorphic posttransplant lymphoproliferative disorder (1), chronic lymphocytic leukemia/small lymphocytic lymphoma (1), marginal zone B-cell lymphoma (1), and low grade B-cell lymphoma (1). Of the 17 SIg-negative cases with amplifiable DNAs, 12 (71%) showed a clonal immunoglobulin heavy chain gene rearrangement. SIg-negative B-cell lymphomas are rare. Complete absence of SIg light chain expression in a mature B cell proliferation can be used as a surrogate marker to help diagnose peripheral B-cell lymphoma.

Prognostic significance of tumour-infiltrating T lymphocytes and T-cell subsets in de novo diffuse large B-cell lymphoma: a multiparameter flow cytometry study

Tumour-infiltrating T lymphocytes (TIL-T) have been implicated in playing a role in controlling tumour growth. We evaluated TIL-T in 55 cases of de novo diffuse large B-cell lymphoma (DLBCL) using three- or four-colour flow cytometric immunophenotyping (FCI). The percentage of TIL-T varied from 3% to 72% of total viable cellular events (mean 32 +/- 20%). The CD4:CD8 ratio varied from 0.17 to 13 (mean 2.3 +/- 2.2). Cases with >/= 20% T cells and those with CD4:CD8 ratios > or = 2.0 showed a significantly better overall survival (P = 0.017 and P = 0.034 respectively). These findings were independent of clinical stage at diagnosis. The T-cell percentage and CD4:CD8 ratio were moderately correlated (Spearman correlation coefficient = 0.47, P = 0.001) and multivariate analysis revealed that the association of the two factors with prognosis was mutually dependent. The T cells in 23 cases were studied for CD45RO. The mean percentage of total T cells expressing CD45RO was 86 +/- 10%. There was a trend towards better survival for those patients with a higher percentage of CD45RO+ T cells (P = 0.06). These results suggest that TIL-T, particularly CD4+ T cells, may play a role in the control of DLBCL, and measurement of T-cell percentage and T-cell subsets using FCI may be useful in predicting the clinical behaviour of DLBCL.

Development of intermediate-grade (mantle cell) and low-grade (small lymphocytic and marginal zone) human non-Hodgkin's lymphomas xenotransplanted in severe combined immunodeficiency mouse models

We have used severe combined immunodeficiency (SCID) (c.b.-17, ICR/SCID) mice to develop xenotransplantation (XT) models for human intermediate-and-low-grade non-Hodgkin's lymphomas (NHL). In the past, SCID mice have provided a variety of useful XT models for human hematopoietic neoplasms that primarily involve the acute leukemias and some nonhematopoietic tumors, but only rare reports exist on use of the SCID mouse model in the study of primary tumor cells from NHL. Intermediate-grade and low-grade NHL are the most common lymphomas seen in adults. There is no effective therapy for those types of NHL, and they have not been established in an animal model to date. The lack of an animal model has hampered studies that can evaluate the disease process in vivo as well as the definition of therapeutic parameters involved in treatment. We report in this study that primary patient samples of NHL ( intermediate grade and low grade) have been successfully established in SCID mice after XT. NHL include intermediate-grade (mantle cell lymphoma) and low-grade (eg, small lymphocytic lymphoma/chronic lymphocytic lymphoma and marginal zone lymphoma) forms. Studies have been directed toward creating appropriate conditions for the optimal grafting of these NHL in SCID mice so that the disease process in humans could be accurately simulated. These studies indicate that development of XT-human lymphoma cells in SCID mice appear to be linked to their biologic and/or clinical behavior, transplanted lymphoma cell number, and age, as well as to the natural killer cell status of the SCID mouse recipients. Evidence has also shown that NHL cells can exhibit homing or trafficking patterns in SCID recipients that resemble those observed in patients with gastrointestinal lymphomatous involvement (particularly that of mantle cell lymphoma). Our studies also indicate that artefactual influences, such as the outgrowth of Epstein-Barr virus-associated lymphoblastoid lesions, are rare occurrences in the human NHL/SCID models that we have established.

Lack of expression of surface immunoglobulin light chains in B-cell non-Hodgkin lymphomas

We describe 10 cases of B-cell non-Hodgkin lymphoma (NHL) that did not express immunoglobulin kappa or lambda light chains by dual-color flow cytometry. Cases were identified from 298 consecutive cases of B-cell NHL and included follicular center cell lymphoma, diffuse large B-cell lymphoma, small noncleaved cell lymphoma, and small lymphocytic lymphoma. One case did not express any immunoglobulin heavy chain (IgH) as well; however, isolated expression of IgG heavy chain was seen in another case. Immunoglobulin heavy chains were not part of the lymphoma panel in other cases. All 3 cases in which gene rearrangement studies were performed showed rearrangement of IgH genes, including the case that did not express surface IgH chains. Immunoglobulin kappa light chain genes were rearranged in 2 of 3 cases and were in germline configuration in the third. All 147 cases of benign lymph nodes analyzed by flow cytometry showed polyclonal expression of immunoglobulin kappa and lambda light chains. Because of the absence of surface immunoglobulin light chains, these tumors must be distinguished from precursor B-cell acute lymphoblastic leukemia, plasma cell tumors, and rare cases of florid follicular hyperplasia that do not express surface immunoglobulins. The absence of immunoglobulin expression on malignant B cells can result from defects at any level from gene transcription to translocation of fully assembled proteins to the cell surface.

Multiparametric immunophenotyping of B cells in peripheral blood of healthy adults by flow cytometry

The investigation of patients suffering from malignant lymphomas of the B-cell type requires flow cytometric immunophenotyping. Several reports described the expression of almost all B lineage antigens on normal and abnormal B lymphocytes. Thus, immunophenotyping of lymphomas must be interpreted in the context of the reference values obtained for healthy control individuals. For this purpose multiparametric flow cytometric analysis offers the unique feature for lymphocyte subset analysis. In the present study B lymphocytes in the peripheral blood of healthy adults were investigated by multiparametric flow cytometric immunophenotyping for the detection of the frequency (in percent) of antigens provided by the revised European-American classification of lymphoid neoplasms (REAL) classification. Thus, 84 healthy adults were investigated and grouped by age (average ages were as follows: group 1, 25.38 years; group 2, 33.86 years; group 3, 44.17 years; group 4, 55.67 years; group 5, 66.67 years). Analysis was done for surface immunoglobulins (kappa and lambda chains of immunoglobulin M [IgM] and IgD) as well as CD10, CD11c, CD23, CD38, CD103, FMC-7, and B-B4. Three-color immunophenotyping was performed for kappa/CD19/CD5, lambda/CD19/CD5, surface IgM/surface IgD/CD19, FMC-7/CD19/CD5, CD103/CD11c/CD19, CD10/CD23/CD19, and CD38/B-B4/CD19 by live gating of CD19+ events (n = 2,000). Although some numerical differences could be obtained for the different groups, statistical differences (P < 0.005) could only be obtained for the CD19+/CD5+ B-cell subset, which was decreased in the elderly patients (group 5). The established two-color and three-color stainings will serve as a basis for future multiparametric immunophenotyping of abnormal lymphocytes (e.g., for patients suffering from non-Hodgkin's lymphoma of the B-cell type).

Accuracy of diagnosis of malignant lymphoma by combining fine-needle aspiration cytomorphology with immunocytochemistry and in selected cases, Southern blotting of aspirated cells: a tissue-controlled study of 86 patients

Fine-needle aspiration (FNA) cytology of lymph nodes in malignant lymphoma is fraught with difficulty. In certain clinical situations, cytology has been documented to be useful in patients with malignant lymphoma. The intent of our investigation was to determine the accuracy of a multiparameter approach in diagnosing lymphoma. We reviewed the results of FNA cytology combined with the immunocytochemistry and, in some cases, the Southern blots of aspirated cell suspensions obtained from 86 suspected lymphoma patients who subsequently underwent surgical biopsy of the aspirated site. In four cases, in which FNA was unable to retrieve sufficient material for diagnosis, the histology showed extensive fibrosis. When the FNA diagnoses were compared with the histologic diagnoses, the diagnosis concurred in 69 cases (56 malignant lymphomas, 12 reactive, 1 atypical lymphoid proliferation). There was one false-positive, six false-negatives, and eight cases diagnosed as atypical lymphoid proliferation. Overall accuracy was 91%. There were two types of false-negative cases: those in which a diagnosis of another malignancy or unspecified malignant neoplasm was made and those that were diagnosed as reactive when the histology showed lymphoma. In seven cases, the DNA rearrangement studies of the antigen receptor genes were successfully performed on the aspirated cells and were useful in establishing lineage and clonality of both B and T lymphoid cells. Our study indicated that the use of a multiparameter approach in the diagnosis of malignant lymphoma by FNA enhanced the accuracy of diagnosis of the non-Hodgkin's lymphomas. In Hodgkin's disease, no benefit was derived from the approach.