Limitations of clonality analysis of B cell proliferations using CDR3 polymerase chain reaction

Use of ultrasensitive RNA in situ hybridization for kappa and lambda light chains assists in the differential diagnosis of B-cell non-Hodgkin and Hodgkin lymphomas in cytopathology practice

Ultrasensitive RNA in situ hybridization for light chain is a relatively new diagnostic tool that aids in the diagnosis of B‐cell lymphomas. The approach has been shown to be as sensitive as flow cytometry in assessing light chain restriction.

Role of immunoglobulin heavy and light chain gene rearrangement analysis in differentiating between benign and malignant bone marrow B-cell lymphoid aggregates

Lymphoid aggregates are found in a minority of bone marrow biopsy and aspirate specimens, and when present, the distinction between benign and malignant aggregates can represent a diagnostic challenge. Morphologic and immunophenotypic evaluation of the aggregates can aid in that distinction but in a few cases, detection of immunoglobulin heavy chain (IGH) and kappa light chain (IGK) gene rearrangements may be needed to rule in or out a malignant disease process. We studied the role of testing for IGH/IGK rearrangements in the distinction between benign and malignant B cell-predominant lymphoid aggregates. Only a few studies have addressed this issue and most lacked an adequate number of cases for establishing statistical significance. Our study retrospectively evaluated 120 bone marrow aspirate and biopsy specimens, 79 cases originally diagnosed with benign lymphoid aggregates [4,5], and 41 demonstrating a B-cell lymphoma with malignant aggregates. Immunohistochemical stains were performed on all cases in our study and flow cytometry results were available in the vast majority of cases (98%). All patients included in our study but 9 had at least 2 years of clinical follow-up information. Of the malignant lymphoma cases, IGH/IGK rearrangements were demonstrated by polymerase chain reaction in 60% of the cases. Moreover, clonal rearrangements were identified in 15% of the cases with benign aggregates. After at least 2 years of follow-up, only one case with a positive clonality study occurring in the setting of morphologically benign-appearing bone marrow lymphoid aggregates experienced a relapse of non-Hodgkin lymphoma. Molecular analysis of the IGH and IGK genes may have utility in confirming the presence of malignancy in bone marrow aspirates and biopsy specimens. False-negative results, however, are possible due to testing limitations and sampling issues. Moreover, patients with conditions such as autoimmune disorders or infectious diseases are shown to also develop clonal B-cell lymphoid aggregates. As a result, we recommend a thorough morphological examination, informative immunohistochemical staining, accurate flow cytometric analysis, and current IGH/IGK rearrangement testing when evaluating bone marrow specimens containing B cell-predominant lymphoid aggregates, with the knowledge that molecular clonality results should be carefully interpreted in the context of morphological and immunophenotypic findings to prevent misdiagnosis.

Experiencia en el uso de protocolos Biomed-2 para el estudio de reordenamientos de TCR e inmunoglobulinas en proliferaciones linfoides en el Instituto Nacional de Cancerología, Colombia

Introducción.

El consorcio europeo BIOMED-2 se creó para determinar si una población linfoide de difícil clasificación patológica es clonal. En Colombia, la implementación de estas pruebas comenzó en el 2015 en el Instituto Nacional de Cancerología E.S.E. (Bogotá).

Objetivos.

Determinar el comportamiento de las pruebas de reordenamiento clonal o clonalidad linfoide. y determinar las dificultades de su uso en nuestro medio verificando su adaptación local y los resultados en una serie retrospectiva de casos y consecutiva de proliferaciones linfoides sometidas a los protocolos BIOMED-2.

Materiales y métodos.

A partir de las historias clínicas, se recolectaron los datos clínicos e histológicos y los resultados de los análisis de los reordenamientos en todos los casos de proliferaciones linfoides sometidas a los protocolos BIOMED-2, entre febrero de 2015 y mayo de 2019.

Resultados.

Se hallaron 132 casos, de los cuales 47 se clasificaron mediante los protocolos de Biomed-2 como hiperplasias linfoides reactivas, 62 como linfomas T, 19 como linfomas B y 3 como neoplasias linfoides de linaje no establecido. Solo en un caso falló la extracción de ADN. Según estos resultados, la mayor dificultad diagnóstica para el patólogo fue el análisis de los infiltrados linfoides T, la mayoría (44) de los cuales correspondía a lesiones cutáneas.

Conclusiones.

Las pruebas de clonalidad pueden usarse en tejidos de diversa calidad en nuestro medio como ayuda en el diagnóstico de proliferaciones linfoides de difícil clasificación. Es importante hacerlas e interpretarlas de manera multidisciplinaria y considerar cada caso por separado.

Diagnostic Accuracy and Prognostic Relevance of Immunoglobulin Heavy Chain Rearrangement and 18F-FDG-PET/CT Compared With Unilateral Bone Marrow Trephination for Detecting Bone Marrow Involvement in Patients With Diffuse Large B-Cell Lymphoma

BACKGROUND

In diffuse large B-cell lymphoma (DLBCL), bone marrow involvement (BMI) has an important clinical implication as a component of staging and International Prognostic Index. This study aimed to determine whether molecular analysis of immunoglobulin heavy chain (IgH) genes and positron emission tomography-computed tomography (PET/CT) could overcome the limitation of defining morphologic BMI by trephination biopsy and could increase the diagnostic accuracy or prognostic prediction.

METHODS

A total of 94 de novo patients with DLBCL underwent PET/CT, polymerase chain reaction (PCR) test for detection of IgH gene rearrangement, and unilateral bone marrow (BM) trephination at diagnosis.

RESULTS

A total of 9 patients (9.6%) were confirmed to present morphologic BMI (mBMI) based on trephination biopsy. On the other hand, 21 patients (22.3%) were confirmed to have IgH clonality (IgH BMI), while 16 (17.0%) were classified with BMI based on the assessment of PET/CT (PET BMI). Each IgH rearrangement PCR and PET/CT showed the high negative predictive value of detecting the BMI. However, the combined assessment of IgH rearrangement and PET/CT could increase the diagnostic accuracy and specificity with 87.2% and 97.0%, respectively. The survival outcome of patients with double positive PET BMI and IgH BMI was significantly worse than that with either single positive PET BMI or IgH BMI, and even less than patients with neither PET BMI nor IgH BMI (3-year PFS: 50.0% vs. 75.4% vs. 97.9%, P = 0.007, 3-year OS: 50.0% vs. 75.6% vs. 80.1%, P = 0.035, respectively).

CONCLUSION

This study suggests that the combined evaluation of PET/CT and IgH rearrangement could give additional information for predicting therapeutic outcomes in patients with negative morphologic BMI as an important part of the prognosis.

Immunohistochemical Profiling of Canine Intestinal T-Cell Lymphomas

Human enteropathy-associated T-cell lymphoma (EATL) is classified into 2 distinct subgroups based on their phenotypes (type I and type II). Canine intestinal T-cell lymphoma can be morphologically classified into large and small cell lymphomas (LCL and SCL, respectively). Their association with human EATL or immunohistochemical and biological features has not been well characterized. In this study, the immunohistochemical profiles of 17 cases of LCL and 33 cases of SCL were evaluated with markers used for human EATL classification. Morphologically, LCL was characterized by sheet-like proliferation of large to moderately sized neoplastic lymphocytes, with scant clear cytoplasm and pleomorphic, irregularly shaped nuclei containing distinctive nucleoli and scattered chromatin. In contrast, SCL was characterized by the proliferation of monomorphic small neoplastic lymphocytes, accompanied by infiltration of nonneoplastic plasma cells. Interestingly, 8 cases demonstrated mixed LCL and SCL morphologies. Granular cytoplasmic expression of granzyme B was observed in most LCL and SCL cases. Membranous expression of CD56 was demonstrated in only 2 of 17 LCL and 0 of 33 SCL cases. Coexpression of CD20 by neoplastic T cells was observed in more SCL cases (16/33; 48%) than LCL cases (1/17; 6%). The CD56-positive cells in 2 cases were negative for CD20. Although canine LCL shares common features with human EATL type I, canine SCL cells and human EATL type II differ in their immunophenotype. Canine intestinal T-cell lymphoma had a homogeneous immunophenotype regardless of cell morphology. The findings of this study may indicate large cell transformation of SCL rather than 2 distinct entities.

Characterization of Feline Immunoglobulin Heavy Chain Variable Region Genes for the Molecular Diagnosis of B-cell Neoplasia

To develop a molecular-based assay so that the diagnosis of feline B-cell neoplasia can be facilitated, we have characterized 24 feline immunoglobulin heavy chain variable region ( IGH V) complementary DNA (cDNA) transcripts. Structural homology with rearranged human IGH V genes was found, and the sequence information was used to design a feline-specific polymerase chain reaction (PCR)-based assay to amplify the complementarity determining region 3 as a marker for B-cell clonality. Conserved primers derived from the second and third framework regions of V gene segments were used in conjunction with 2 sequence-specific primers and 1 degenerate primer derived from the J gene segments. Each PCR reaction was run in duplicate, and both native and denatured PCR products were evaluated using polyacrylamide gel electrophoresis. Formalin-fixed, paraffin-embedded (FFPE) tissue sections from cats with confirmed B-cell neoplasia (diffuse large B-cell lymphoma, plasmacytoma, and myeloma) were examined, and 15/22 (68.2%) cats produced results indicative of the presence of a monoclonal population of B cells. The evaluation of denatured PCR products (heteroduplex analysis) facilitated a more accurate interpretation in 3/15 (20%) cats. Pseudoclonality was a major reason for the failure to detect monoclonality. Poor DNA quality is a significant concern and was responsible for the removal of 2 cats from the study. Using this assay, FFPE normal feline lymphoid tissues and unfixed peripheral blood mononuclear cells were determined to be composed of polyclonal populations of B cells. This assay represents a useful adjunctive diagnostic tool for the diagnosis and investigation of feline B-cell lymphoproliferative disorders.

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.

Association between lymphocyte antigen receptor gene rearrangements and histopathological evaluation in canine chronic enteropathy

Although definitive diagnosis of chronic enteropathy (CE) and gastrointestinal (GI) lymphoma requires histopathological evaluation of the GI tract, these conditions are often still difficult to differentiate from each other. Polymerase chain reaction (PCR) for antigen receptor gene rearrangements (PARR) has been applied recently as an adjunctive for diagnosis of lymphoid tumors; however, its clinical value in canine CE and GI lymphoma remains unclear. The purpose of this study was to investigate the relationship between PARR and histopathological diagnosis, degree of enteritis or lymphoma, and long-term prognosis in dogs, in order to evaluate the clinical significance of PARR. Endoscopic biopsy specimens obtained from 96 dogs with chronic enteritis (mild, n=14; moderate, n=20; marked, n=62) and 21 dogs with GI lymphoma were used. Clonality was observed in 51% of the animals with chronic enteritis; interestingly, it was found in 29% of those with only mild enteritis. In dogs with marked enteritis, the rate of PARR was higher in those with lymphocyte epitheliotropism than in those without epitheliotropism. The sensitivity of PARR in animals with GI lymphoma was 76%. There was no significant prognostic difference between chronic enteritis with or without clonal rearrangements. In contrast, dogs histopathologically diagnosed with marked enteritis had a significantly shorter survival time than did those with mild or moderate enteritis. While the significance of PARR in the diagnosis of GI lymphoma remains uncertain, the pathological roles of clonally expanding lymphocytes in canine CE should be investigated further.

Clonality analysis of lymphoid proliferations using the BIOMED-2 clonality assays: a single institution experience

Background

Clonality determination in patients with lymphoproliferative disorders can improve the final diagnosis. The aim of our study was to evaluate the applicative value of standardized BIOMED-2 gene clonality assay protocols for the analysis of clonality of lymphocytes in a group of different lymphoid proliferations.

Materials and methods.

With this purpose, 121 specimens from 91 patients with suspected lymphoproliferations submitted for routine diagnostics from January to December 2011 were retrospectively analyzed. According to the final diagnosis, our series comprised 32 cases of B-cell lymphomas, 38 cases of non-Hodgkin’s T-cell lymphomas and 51 cases of reactive lymphoid proliferations. Clonality testing was performed using the BIOMED-2 clonality assays.

Results

The determined sensitivity of the TCR assay was 91.9%, while the sensitivity of the IGH assay was 74.2%. The determined specificity of the IGH assay was 73.3% in the group of lymphomas and 87.2% in the group of reactive lesions. The determined specificity of the TCR assay was 62.5% in the group of lymphomas and 54.3% in the group of reactive lesions.

Conclusions

In the present study, we confirmed the utility of standardized BIOMED-2 clonality assays for the detection of clonality in a routine diagnostical setting of non-Hodgkin’s lymphomas. Reactions for the detection of the complete IGH rearrangements and reactions for the detection of the TCR rearrangements are a good choice for clonality testing of a wide range of lymphoid proliferations and specimen types while the reactions for the detection of incomplete IGH rearrangements have not shown any additional diagnostic value.

Ultrasensitive RNA in situ hybridization for detection of restricted clonal expression of low-abundance immunoglobulin light chain mRNA in B-cell lymphoproliferative disorders

OBJECTIVES

To assess the feasibility of using a novel ultrasensitive bright-field in situ hybridization approach (BRISH) to evaluate κ and λ immunoglobulin messenger RNA (mRNA) expression in situ in B-cell non-Hodgkin lymphoma (NHL).

METHODS

A series of 110 semiconsecutive clinical cases evaluated for lymphoma with historic flow cytometric (FCM) results were assessed with BRISH.

RESULTS

BRISH light chain restriction (LCR) results were concordant with FCM in 108 (99%) of 109 evaluable cases. Additional small B-cell lymphoma cohorts were successfully evaluated.

CONCLUSIONS

BRISH analysis of κ and λ immunoglobulin mRNA expression is a sensitive tool for establishing LCR in B-cell NHL when FCM results are not available.

Dried blood spot sampling for detection of monoclonal immunoglobulin gene rearrangement

Molecular methods are important tools for diagnosis and monitoring of many lymphoproliferative disorders. The reliability of lymphoma diagnoses is strikingly different between developed and developing countries, partly due to lack of access to these advanced molecular analyses. To overcome these problems, we propose a new application of dried blood spots (DBS) for detecting clonal B-cell populations in peripheral blood (PB). We ensured that the DBS contained sufficient lymphocytes to perform a PCR-based clonality assay without producing false positives. Using the Namalwa B-cell line, we established that the assay is sensitive enough to detect 200 clonal cells in the analyzed sample. Very similar clonal results were obtained between DNA from DBS and fresh whole blood from patients with B-cell chronic lymphocytic leukemia. B-cell clonality can also be detected in DBS from African children with EBV-associated diseases. This is the first study demonstrating that clonality testing can be performed on DBS samples, thus improving the diagnostic and monitoring options for lymphoproliferative diseases in resource-limited settings.

A simple and efficient method for DNA extraction from skin and paraffin-embedded tissues applicable to T-cell clonality assays

PCR-based clonality assay of rearranged T-cell receptor genes gamma and beta (TCRG and TCRB) in a number of cases could be essential to discriminate between cutaneous T-cell lymphomas and reactive lymphoproliferative lesions in the skin. However, extraction of good-quality DNA from skin specimens (especially formalin-fixed paraffin-embedded) remains a challenge. Common procedures, being labour-intensive and time-consuming and requiring toxic solvents such as phenol and chloroform, still may end up with DNA sample of insufficient quality. We herewith present a simple and efficient method for DNA isolation based on ammonia extraction of tissue, followed by neutralization and simultaneous salting out of proteins with acetic acid. We have analysed 30 samples - 24 fresh (16 skin, two spleen and six lymph node) and six paraffin-embedded. Standard procedure (proteinase K digestion, followed by phenol/chloroform extraction) has been carried out simultaneously. We observed good PCR signal for TCRG rearrangements in 30 samples processed with the new protocol and only in 20 extracted with proteinase K/phenol/chloroform. For TCRB, the success rate was 29 of 30 with the new protocol, compared to 11 of 30 with conventional protocol. The proposed method of DNA extraction should improve the value of T-cell clonality assay, because insufficient DNA quality and quantity may bias analysis towards monoclonality and therefore cause false-positive results.

Presence of monoclonal T-cell populations in B-cell post-transplant lymphoproliferative disorders

As has been previously shown, the lack of immune surveillance plays a major role in the unchecked proliferation of Epstein-Barr virus (EBV)-infected B cells in the pathogenesis of B-cell post-transplant lymphoproliferative disorders. We hypothesised that the lack of immune surveillance should possibly also affect T cells, and this should lead to subsequent emergence of T-cell clones. The presence of both B- and T-cell clones in post-transplant lymphoproliferative disorders samples has rarely been demonstrated in the past. We systematically evaluated 26 B-cell post-transplant lymphoproliferative disorder, 23 human immune deficiency virus-associated B-cell lymphoma and 10 immune-competent diffuse large B-cell lymphoma samples for B- and T-cell clonality (polymerase chain reaction and heteroduplex analysis using BIOMED-2 protocol), T-cell subsets (immunohistochemistry) and EBV association (in situ hybridisation using EBER). One-half of B-cell post-transplant lymphoproliferative disorders showed evidence of monoclonal T-cell expansion, and among the T cells present in the tissue samples, CD8-positive cells predominated. Although 9/13 (69%) B-cell post-transplant lymphoproliferative disorders with the presence of monoclonal T-cell population had a CD4:CD8 ratio of ≤0.4, 0/13 of the cases without monoclonal T-cell expansion had a ratio ≤0.4 (P = 0.002). Only 2/26 (8%) demonstrated significant cytological atypia in the CD3/CD8-positive cells. There was no association between EBV and presence of T-cell clones. T-cell clones were not identified in lymphomas other than B-cell post-transplant lymphoproliferative disorders. Among 53.8% cases of EBV-positive B-cell post-transplant lymphoproliferative disorders with associated clonal expansion of T-cells tested, none had EBV-positive T cells. We conclude that half of B-cell post-transplant lymphoproliferative disorders are associated with clonal expansion of CD8-positive T cells, most of which do not amount to the coexistence of a T-cell post-transplant lymphoproliferative disorders.

Fresh-frozen, optimal cutting temperature (OCT) compound-embedded bone marrow aspirates: a reliable resource for morphological, immunohistochemical and molecular examinations

The usefulness of fresh-frozen, optimal cutting temperature (OCT) compound-embedded (FFOE) bone marrow (BM) aspirates was evaluated as a reliable resource for morphological, immunohistochemical and molecular examinations. One hundred BM aspirates were collected in polypropylene tubes and immediately frozen for 2 h in a deep freezer. Frozen BM was transferred to a cryomold filled with OCT compound and the prepared samples were stored in a deep freezer. Histological examination and immunohistochemical staining, polymerase chain reaction (PCR), sequencing and reverse transcription (RT)-PCR were performed to evaluate the quality of the FFOE BM sections in 10% of randomly selected samples. FFOE BM sections revealed better morphologies than paraffin-embedded clot sections in haematoxylin and eosin staining because mature erythrocytes were removed during the staining process in frozen BM sections. Immunohistochemical staining for CD34 revealed excellent staining quality and oil red O staining showed that fat vacuoles in cells were well preserved. The quality of genomic DNA in FFOE BM sections was suitable for obtaining about 2000 bp PCR product for the human leucocyte antigen-A locus followed by direct sequencing of the sample, and the quality of total RNA was suitable for detection of BCR-ABL fusion transcript. FFOE BM aspirates are a reliable resource for various laboratory tests of diagnostic and research arenas.

DNA amplification from formalin-fixed decalcified paraffin-embedded bone marrow trephine specimens: does the duration of storage matter?

INTRODUCTION

Examination of bone marrow (BM) trephines has been traditionally limited to histological analysis. With renewed interest in their use in molecular diagnostics, studies assessing the impact of duration of storage on DNA amplification from archived BM trephines are required.

METHODS

DNA extraction was performed on 169 formalin-fixed decalcified paraffin-embedded (FFDPE) trephine blocks with a mean duration of storage of 59.4 months (range 4-200 months). An amplification control master mix from the In Vivo Scribe Immunoglobulin Heavy Chain Clonality kit was used to determine DNA amplification at different amplicon sizes [96-600 base pairs (bp)].

RESULTS

Amplification at 96 bp was noted in 145 of 169 specimens (85.8%). Progressive reduction in amplification was noted at higher base pairs with 99 of 169 (58.6%) amplifying at 200 bp, 56 cases (33.1%) at 300 bp, 35 (20.7%) at 400 bp and 19 (11.2%) at 600 bp. The impact of duration of storage on DNA amplification was not statistically significant.

CONCLUSIONS

DNA was obtained from archival BM trephine specimens in approximately 86% of cases, indicating good potential for utilisation in polymerase chain reaction (PCR) techniques. The duration of storage of FFDPE tissue had no impact on the ability to amplify specimens.

The frequency of immunoglobulin heavy chain gene and T-cell receptor gamma-chain gene rearrangements and Epstein-Barr virus in ALK+ and ALK- anaplastic large cell lymphoma and other peripheral T-cell lymphomas

We previously identified a relatively high frequency of B-cell proliferations along with simultaneous T-cell receptor gamma-chain gene (TRG) and immunoglobulin heavy chain gene (IGH) rearrangements in a series of angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma, unspecified. Here, we report on a series of 74 peripheral T-cell lymphoma (PTCL) cases composed entirely of specific PTCL subtypes, including 28 cases of ALK+ anaplastic large-cell lymphoma (ALCL), 35 cases of ALK- ALCL, and 11 cases that represent other specific PTCL subtypes. We performed IGH and TRG gene rearrangement studies and in situ hybridization for Epstein-Barr virus (EBV) to determine the frequency of IGH clonality and to investigate the relationship between EBV, clonality, and associated B-cell proliferations. Using BIOMED-2 PCR assays, we detected TRG clones in 64 of 74 (86%) cases and IGH clones in 6 of 74 (8%) cases, with all IGH-positive cases exhibiting a concurrent TRG clone. Despite the detection of occasional IGH clones, there was no correlation between IGH clonality and EBV, and B-cell proliferations were not identified in any of the cases. These findings suggest that other factors contribute to IGH clonality and demonstrate that, in the absence of an associated B-cell proliferation, IGH clonality occurs infrequently (8%) in specific PTCL subtypes.

Optimization of PCR amplification for B- and T-cell clonality analysis on formalin-fixed and paraffin-embedded samples

In many cases, particularly in retrospective studies, only formalin-fixed and paraffin-embedded (FFPE) tissue samples are available for molecular studies. DNA recovered from FFPE tissues generally consists of fragmented small target sequences with chemical alterations. Clonality analysis is not easy on FFPE samples, in fact, it requires even more experience than that of performed on fresh samples or is more complicated than most genomic PCR amplifications for somatic genes. In our study, we have performed a multi-parameter PCR evaluation investigating immunoglobulin heavy chain gene (IgH) and T-cell receptor gamma gene (TCRgamma) rearrangements on non-purified crude lysates of FFPE samples, in order to establish the significance of different variables on performance of PCR amplification. The results showed that a slight decrease in the concentration of primers in combination with a slight increase in MgCl2 and Taq polymerase concentrations, as well as the use diluted crude template and a standard amount of dNTPs can be the modifications of choice while adjusting IgH and TCRgamma clonality tests on poor quality DNA FFPE samples. Using our improved protocol, 74% (17/23) of the tested B-cell lymphomas and 68% (31/46) of the tested T-cell lymphomas demonstrated monoclonal PCR product, proving the applicability of our optimized method. Our experience may be of help during the optimization process in technically difficult cases as well as to determine which parameters and how should be changed to minimize false-negative and false-positive results.

Erythema migrans: a reassessment of diagnostic criteria for early cutaneous manifestations of borreliosis with particular emphasis on clonality investigations

BACKGROUND

Controversy exists about the relationship of borrelia infection with B-cell lymphomas because B-cell clonality has been identified in infiltrates that contained borrelia-specific DNA. Systematic clinicopathological, immunophenotypical and molecular pathological studies of early borreliosis are lacking.

OBJECTIVES

(i) To clarify whether clonal B-cell populations are present already in early borreliosis of the skin (erythema migrans); (ii) to re-evaluate clinicopathological, immunophenotypical and molecular pathological criteria for diagnosis of erythema migrans.

METHODS

Study of 34 patients with erythema migrans confirmed by polymerase chain reaction (PCR). Infiltrates were analysed by histopathological and immunohistochemical methods and multiplex PCR for clonal IgH rearrangements.

RESULTS

Erythema migrans shows a broad spectrum of changes including sparse infiltrates of T lymphocytes, dense interstitial granulomatous infiltrates (CD68+), and pseudolymphomatous patterns with germinal centre formation. There were accompanying epidermal changes in 59% of patients, and plasma cells were an inconsistent finding. B cells were few when infiltrates were sparse, but increased disproportionately when infiltrates were dense. IgH rearrangement studies revealed one pseudo-oligoclonal, three pseudoclonal and three clonal infiltrates. Pseudoclonality was encountered when infiltrates contained only few B lymphocytes.

CONCLUSIONS

Infiltrates in erythema migrans are dominated by T cells followed by CD68+ histiocytes and B lymphocytes. Plasma cells are an inconsistent finding. Pseudoclonality of IgH rearrangement is a result of infiltrates being sparse in B lymphocytes and represents a pitfall in molecular pathological diagnosis that can only be avoided by duplicate or triplicate tests. Incidental B-cell clonality may be encountered in patients with unequivocal erythema migrans and should not be interpreted as a malignant lymphomatous process induced by borrelia.

Bone marrow trephines containing lymphoid aggregates from patients with rheumatoid and other autoimmune disorders frequently show clonal B-cell infiltrates

In bone marrow trephines, morphological and immunohistochemical criteria may not be sufficient to discriminate reactive from malignant lymphoid infiltrates. The aim of this study was to determine whether the detection of clonal immunoglobulin heavy chain (IGH) gene rearrangements is a reliable and specific marker for malignant B-cell clones in bone marrow biopsies. Bone marrow trephines with infiltration by different types of low-grade B-cell non-Hodgkin lymphoma (n = 32), reactive lymphoid hyperplasia (n = 18), and reactive lymphoid aggregates (n = 15), including 5 patients with rheumatoid or other autoimmune disorders, were analyzed by morphology, immunohistochemistry, IGH gene rearrangement (polymerase chain reaction), and DNA sequence analysis in selected cases. In 22 (68.8%) of 32 patients with B-cell non-Hodgkin lymphoma, a clonal IGH gene rearrangement was detected. Of the reactive cases, 1 of 18 patients with lymphoid hyperplasia demonstrated clonality, and 9 (60%) of 15 patients with reactive lymphoid aggregates gave a clonal result (GeneScan analysis). DNA sequence analysis was performed in 7 of the latter patients confirming clonality in 6. Four of the patients with B-cell clonality had an autoimmune disorder. None of these patients developed a malignant lymphoma during follow-up. Thus, the molecular detection of a clonal rearrangement of the IGH gene may support the diagnosis of a malignant lymphoma infiltrating the bone marrow. However, morphologically and immunohistochemically benign lymphoid aggregates might also harbor B-cell clones especially in patients with autoimmune disorders. Therefore, the detection of clonality has to be interpreted with utmost care and does not qualify for the unequivocal diagnosis of a malignant B-cell lymphoma.

Protocol for the use of polymerase chain reaction in the detection of intraocular large B-cell lymphoma in ocular samples

To determine the usefulness of polymerase chain reaction (PCR) analyses in the diagnosis of lymphoid infiltrate cells in ocular samples, PCR was performed using oligonucleotide primers specific for immunoglobulin heavy chain rearrangement at framework 2, framework 3, and t(14;18) translocation of the bcl-2 gene. These were used to successfully generate amplicons of 220 to 230 bp, 110 to 120 bp, and 175 to 200 bp, respectively. After PCR amplification, primers directed against the t(14;18) detected 10 pg of B-cell lymphoma DNA. PCR against Fr2 and Fr3 IgH rearrangement detected 10 fg and 10 pg in the seminested PCR, respectively. Conventional pathological methods were highly accurate at establishing the correct final diagnosis in formalin-fixed, paraffin-embedded samples but were much less sensitive and predictive in cytological specimens of intraocular fluid. A combination of the three PCR reactions was an equally successful diagnostic approach on paraffin-embedded samples, whereas single PCR reactions did not significantly improve diagnosis over histopathological diagnostic techniques. Thus, a combination of PCR reactions is useful in the detection of B-cell monoclonality, aids the differentiation between lymphomatous and inflammatory infiltrates, and is more powerful as a diagnostic method than single PCR or conventional cytopathology for lymphoid infiltrates in ocular fluid aspirates.

High-dose methotrexate is beneficial in parenchymal brain masses of uncertain origin suspicious for primary CNS lymphoma

In patients with parenchymal brain masses of uncertain origin responsive to corticosteroids, primary CNS lymphoma (PCNSL) should be considered. PCNSL is a rare but aggressive brain tumor that is highly sensitive to high-dose methotrexate (HDMTX)-based chemotherapy. We report a series of six patients with brain masses without histologic confirmation suspicious for PCNSL based on clinical and radiomorphologic criteria after exclusion of some infectious conditions. All patients were treated with HDMTX. We observed two complete responses, two partial responses, and one stable disease. One patient had progressive disease and received rescue whole-brain irradiation. All patients were alive without disease progression 12-48 months after HDMTX start. No symptoms of late neurotoxicity have occurred so far. The response and survival data in this small series of patients are encouraging and suggest a benefit for patients with suspected PCNSL after initial treatment with HDMTX.

Multiplex polymerase chain reaction on FTA cards vs. flow cytometry for B-lymphocyte clonality

BACKGROUND

Two-colour flow cytometry was compared with multiplex PCR with capillary electrophoresis for clonality determination in specific categories of B-cell lymphoma. FTA cards were evaluated for preserving DNA from node imprints and expediting molecular analysis.

METHODS

A single-tube multiplex PCR targeted IGH and lymphoma-specific translocations in DNA extracted from 180 frozen lymphoid tissues and DNA bound to FTA cards from 192 fresh tissues and 137 aspirates. PCR results were compared with flow cytometry in the extracted and aspirated samples.

RESULTS

Overall, single-tube multiplex PCR sensitivity was equivalent in the sample groups (intergroup range 79%-91%). False negatives were associated with tumour origin in the follicle centre. Multiplex PCR and flow cytometry were equally sensitive and together detected 98% of B-cell lymphomas. Additional two-tube targeting of IGK suggested an overall molecular sensitivity >90%. False positive (pseudoclonal) single-tube multiplex PCR was associated with necrosis and sparse lymphocytes.

CONCLUSIONS

Multiplex PCR using template DNA bound to an FTA card effectively detects B-lymphocyte clonality, obviates DNA extraction and refrigeration, and can be used without diminished sensitivity in fine needle aspirates or node imprints as a replacement for or complement to flow cytometry at any point in the diagnostic work-up.

Improved reliability of lymphoma diagnostics via PCR-based clonality testing: — Report of the BIOMED-2 Concerted Action BHM4-CT98-3936

The diagnosis of malignant lymphoma is a recognized difficult area in histopathology. Therefore, detection of clonality in a suspected lymphoproliferation is a valuable diagnostic criterion. We have developed primer sets for the detection of rearrangements in the B- and T-cell receptor genes as reliable tools for clonality assessment in lymphoproliferations suspected for lymphoma. In this issue of Leukemia, the participants of the BIOMED-2 Concerted Action CT98-3936 report on the validation of the newly developed clonality assays in various disease entities. Clonality was detected in 99% of all B-cell malignancies and in 94% of all T-cell malignancies, whereas the great majority of reactive lesions showed polyclonality. The combined BIOMED-2 results are summarized in a guideline, which can now be implemented in routine lymphoma diagnostics. The use of this standardized approach in patients with a suspect lymphoproliferation will result in improved diagnosis of malignant lymphoma.

Splitting bone marrow trephines into frozen and fixed fragments allows parallel histological and molecular detection of B cell malignant infiltrates

Clonality analysis of the immunoglobulin heavy chain (IgH) gene is helpful in identifying malignant B cell infiltrates in the bone marrow and is usually carried out on separate aspirates or on the same formalin-fixed decalcified bone marrow specimen. To determine whether the removal of the decalcification step would improve the molecular analysis, we first studied 12 bone marrow specimens with lymphoma infiltration split into a fixed and a small frozen fragment. Both the detection rate of IgH gene monoclonality and DNA quality were found to be superior in the frozen part than in the fixed part. Conversely, to evaluate whether the split would compromise histological analysis, we selected a series of 134 bone marrow specimens obtained from patients with small B cell lymphoma and showing IgH monoclonality on the frozen part. The histological detection rate of infiltrated or suspicious infiltrates (95%) on the fixed part was not altered by saving a frozen part.

Immunoglobulin gene rearrangement analysis in cerebrospinal fluid of patients with lymphoproliferative processes

OBJECTIVE

To determine the sensitivity and specificity of clonal immunoglobulin heavy chain gene rearrangement (IGHR) analysis in the distinction of benign and malignant lymphoproliferative diseases.

METHODS

A retrospective analysis was conducted of patients in whom a malignant lymphoproliferative process was suspected. Cells of CSF samples were collected by centrifugation, resuspended in 100 microl of the supernatant and boiled. A 10 microl aliquot of this lysate served as template for semi-nested polymerase chain reaction using variable and joining region consensus primers. PCR products were analyzed by polyacrylamide gel electrophoresis. Cytopathological diagnosis and flow cytometry results were recorded. Sensitivity and specificity of IGHR analysis, cytopathology and flow cytometry were calculated.

RESULTS

Eleven patients (12 specimens) had involvement of leptomeninges at the time of lumbar puncture. Another 25 cases (27 specimens) had normal CSF findings or were diagnosed with benign lymphoproliferative conditions. Sensitivity of CSF cytopathology, flow cytometry and IGHR analysis were 0.27 [95% confidence interval 0.06, 0.61], 0.1 [0.003, 0.45] and 0.58 [0.28, 0.85]. Specificity was 1 [0.86, 1], 0.95 [0.77, 1.0] and 0.85 [0.66, 0.96].

INTERPRETATION

IGHR analysis appears to be a useful addition to morphological and flow cytometry analysis of cerebrospinal fluid in the evaluation of CNS lymphoproliferative processes.

Application of BIOMED-2 primers in fixed and decalcified bone marrow biopsies: analysis of immunoglobulin H receptor rearrangements in B-cell non-Hodgkin's lymphomas

The detection of clonality in lymphomas was recently improved by the BIOMED-2 approach, but analysis of fixed tissues is limited. Here, we adapted the BIOMED-2 protocol for examining immunoglobulin H (IgH) receptor rearrangements in fixed, decalcified bone marrow biopsies (BMBs) for clonality analysis in B-cell non-Hodgkin's lymphomas (B-NHL). The study included 111 decalcified BMBs (12 formalin fixed and 99 glutardialdehyde fixed), with B-NHL (n = 85), T-NHL (n = 8), or reactive infiltrates (n = 18). Initially, IgH FRIII polymerase chain reaction (PCR) analysis of crude DNA extracts from 75 glutardialdehyde-fixed BMBs (B-NHLs) using a standard seminested PCR resulted in clonal peaks in 46 of 75 (61.3%) BMBs compared with 19 of 70 (27.1%) for the original BIOMED-2 protocol. Modifications to both DNA extraction and PCR reaction improved the detection rate to 26 of 36 (72.2%) for BIOMED-2 primers, including 10 of 15 (66.7%) cases not detected by our standard IgH analysis. Moreover, introducing the same modifications for analysis of the FRII region by BIOMED-2 primers revealed clonal peaks in 19 of 36 (52.8%) B-NHLs compared with 5 of 70 (7.1%) for the original BIOMED-2 protocol. Together, analysis of FRII and FRIII regions by the modified BIOMED-2 protocol increased the detection rate to 31 of 36 (86.1%), particularly for BMBs with histological evidence of follicular lymphoma (FRIII, 70%; FRII, 90%). In summary, this study provides an improved protocol for detection of clonality by IgH-specific BIOMED-2 primers in fixed, decalcified bone marrow biopsies.

Ancillary techniques in bone marrow pathology: molecular diagnostics on bone marrow trephine biopsies

Pathologic examination of trephine bone marrow (BM) biopsies plays a central role in the diagnosis and staging of haematological neoplasms and other disorders affecting haematopoiesis. Haematopathology has been profoundly influenced by the advent of molecular genetic techniques suitable for paraffin-embedded tissues, and certain applications, such as the determination of B- and T-cell clonality, belong to its standard diagnostic repertoire. Many of these molecular tests can be performed successfully with nucleic acids extracted from BM trephine biopsies, if some technical aspects specific to this template source such as various fixation and decalcification procedures are taken into consideration. The current indications for molecular BM diagnostics range from the confirmation of lymphoma involvement with gene rearrangement analysis, demonstration of tumor-specific translocations in lymphoid and chronic myeloproliferative disorders along to the detection of microorganisms or marrow involvement by soft tissue sarcomas. The availability of quantitative polymerase chain reaction techniques for the investigation of allelic imbalances and gene expression levels in paraffin-embedded material also open new avenues for research and advanced diagnostics. The molecular detection of minimal residual disease in haematological neoplasms, especially in the context of new treatment strategies, will provide future challenges. This article summarizes the current state of the art in molecular diagnostics applied to paraffin-embedded BM biopsies.

Molecular analysis of B-cell clonality in Helicobacter pylori gastritis

The aim of our study was to identify PCR-detectable clonal B-cell population in Helicobacter pylori gastritis and assess their relation to the Wotherspoon-Isaacson (W-I) grade for gastric lymphoid infiltrates. Amplified DNA was obtained from thirty four H. pylori positive gastritis dyspeptic patients and thirty four H. pylori negative matched controls. Clonal bands were observed in 6 (2/17 W-I Grade 1, 2/13 W-I Grade 2, and 2/4 W-I Grade 3 lesions) and polyclonal smears in 24 cases (15 W-I Grade 1, 7 W-I Grade 2, and 2 W-I Grade 3). Four additional W-I Grade 2 samples with clonal bands were associated with background polyclonal smear and were not reproducible. Clonal bands were not recorded in controls. B-cell clonality was not related to W-I grades. We conclude that certain H. pylori positive gastritis patients show PCR-detectable monoclonality, which is independent of the W-I grade of gastritis and cannot be taken as evidence of an existing neoplastic lesion.

Application of a fluorescent PCR method for molecular diagnosis of posttransplant lymphoproliferative disorders on routine tissue sections

Molecular detection of monoclonality can play an important role in the diagnosis of posttransplantation lymphoproliferative disorders (PTLD). To permit accurate molecular diagnosis of PTLD even on very small amounts of DNA extracted from routinely embedded histologic material, we adapted a commercially available PCR protocol (for FR-1, -2 and -3 regions), originally designed for use on fresh/frozen samples. We applied this approach on routine biopsy/surgical material of 10 PTLD (from nine patients). All three FR regions were always amplified, indicating that the extracted DNA was of medium quality. All five PTLD morphologically classified as lymphomas were monoclonal in at least one FR region. Thus, using the WHO histologic, immunohistochemical, and clinical criteria as the reference standard, the approach provided 100% sensitivity for detection of monoclonal malignancies, supporting the validity of the method. Of five specimens classified morphologically as polymorphic PTLD, three displayed a solitary IgH gene rearrangement peak, consistent with the presence of a monoclonal B-cell population (ie, monoclonal polymorphic PTLD). This rapid and straightforward procedure, which allows identification of a wide range of IgH rearrangements, could facilitate molecular analysis of PTLD in routine practice, while limiting consumption of valuable diagnostic material.

Characterization of feline T cell receptor gamma (TCRG) variable region genes for the molecular diagnosis of feline intestinal T cell lymphoma

A diagnosis of intestinal lymphoma is currently made on the basis of clinical and morphologic criteria. This can prove problematic for many reasons that include inadequate sample size, the coexistence of lymphoma and inflammation, and the inability to assess architectural integrity of all tissue compartments in biopsy specimens obtained endoscopically. The detection of a clonal population of cells in a lymphoproliferative lesion represents an important criterion for the diagnosis of neoplasia, but this has not been assessed in feline intestinal lymphoma. T cell receptor gamma (TCRG) gene rearrangement analysis using polymerase chain reaction (PCR) is a methodology that can be used to detect clonality in T cell populations. The basis of this assay depends on the assessment of the junctional diversity that results from rearrangement of TCRG V (variable) and J (joining) gene segments. Feline TCRG transcripts from normal small intestine and spleen were obtained using a rapid amplification of cDNA ends (5'RACE) method. Limited diversity of TCRG V and J gene segments was observed. The high degree of sequence homology in the TCRG V and J gene segments was exploited to develop a PCR test for the assessment of TCRG V--J junctional diversity and hence clonality determination of T cell populations in cats. Molecular clonality determination was applied to feline intestinal lymphoplasmacytic inflammatory bowel disease (IBD) (9 cats), and transmural and mucosal T cell lymphoma (28 cats). Clonal rearrangement of the TCRG V--J junction was detected in 22 of 28 intestinal T cell lymphomas, and oligoclonality was detected in 3 intestinal T cell lymphomas. This contrasted with the detection of polyclonal rearrangement in normal intestinal tissues (3 cats) and in lymphoplasmacytic IBD (9 cats). It is proposed that assessment of TCRG V--J junctional diversity for the detection of clonality represents an important adjunctive tool for the diagnosis of T cell lymphoma in the cat.

Rapid diagnosis of clonal immunoglobulin heavy chain gene rearrangements in cutaneous B-cell lymphomas using the LightCycler-Polymerase Chain Reaction with DNA melting curve analysis

We have recently developed a novel Immunoglobulin heavy chain gene rearrangement (IgH-R) assay that combines polymerase chain reaction (PCR) amplification and analysis in the same closed capillary tube using the LightCycler System. IgH-R can be identified by DNA melting curve analysis within 40 minutes after DNA preparation and amplification. To test the clinical utility of this new IgH-R assay for rapidly diagnosing cutaneous B-cell lymphomas, we prospectively analyzed 44 formalin-fixed, paraffin-embedded tissues suspected of B-cell malignant lymphoma: skin (n = 31), lymph node (n = 7), stomach (n = 3), spleen (n = 1), colon (n = 1), and soft tissue (n = 1). We detected IgH-R in 12 DNA samples, including 8 skin biopsies, with the following diagnoses: B-cell chronic lymphocytic leukemia (n = 4), extranodal marginal zone B-cell lymphoma (n = 4), diffuse large B-cell lymphoma (n = 2), Burkitt lymphoma (n = 1), and precursor B-lymphoblastic lymphoma (n = 1). DNA melting curve analysis, compared with polyacrylamide gel electrophoresis, achieved a sensitivity equal to 92.3% and a specificity equal to 100%. There was a single false negative result because DNA melting curve analysis could not detect less than 10.0% clonal B-cells. We conclude that this new, rapid PCR assay for detecting IgH-R based on DNA melting curve analysis can be clinically useful for confirming the initial diagnosis of B-cell malignant lymphoma.

Design and standardization of PCR primers and protocols for detection of clonal immunoglobulin and T-cell receptor gene recombinations in suspect lymphoproliferations: report of the BIOMED-2 Concerted Action BMH4-CT98-3936

In a European BIOMED-2 collaborative study, multiplex PCR assays have successfully been developed and standardized for the detection of clonally rearranged immunoglobulin (Ig) and T-cell receptor (TCR) genes and the chromosome aberrations t(11;14) and t(14;18). This has resulted in 107 different primers in only 18 multiplex PCR tubes: three VH-JH, two DH-JH, two Ig kappa (IGK), one Ig lambda (IGL), three TCR beta (TCRB), two TCR gamma (TCRG), one TCR delta (TCRD), three BCL1-Ig heavy chain (IGH), and one BCL2-IGH. The PCR products of Ig/TCR genes can be analyzed for clonality assessment by heteroduplex analysis or GeneScanning. The detection rate of clonal rearrangements using the BIOMED-2 primer sets is unprecedentedly high. This is mainly based on the complementarity of the various BIOMED-2 tubes. In particular, combined application of IGH (VH-JH and DH-JH) and IGK tubes can detect virtually all clonal B-cell proliferations, even in B-cell malignancies with high levels of somatic mutations. The contribution of IGL gene rearrangements seems limited. Combined usage of the TCRB and TCRG tubes detects virtually all clonal T-cell populations, whereas the TCRD tube has added value in case of TCRgammadelta(+) T-cell proliferations. The BIOMED-2 multiplex tubes can now be used for diagnostic clonality studies as well as for the identification of PCR targets suitable for the detection of minimal residual disease.

Improved detection of clonality in cutaneous T-cell lymphomas using laser capture microdissection

BACKGROUND

The diagnosis of cutaneous T-cell lymphoma is a challenge for both the pathologist and the clinician. This is particularly true for distinguishing early-stage mycosis fungoides from dermatitis. In this clinical setting, the presence of a clonal T-cell population supports lymphoma.

METHODS

Usually, routinely processed paraffin-embedded material is available for gene rearrangement analysis, and polymerase chain reaction (PCR)-based methods to assess clonality can be performed. One drawback of this approach is that sensitivity is suboptimal in biopsy specimens in which the lymphocytic infiltrate represents only a small percentage of all cells present. Another drawback is that DNA extraction from routinely processed, paraffin-embedded tissue is a time-consuming and labor-intensive procedure which can take up to 5 days in our laboratory. To bypass these problems, we used laser capture microdissection (LCM) to obtain lymphocytic infiltrates from tissue sections of formalin-fixed, paraffin-embedded skin biopsy specimens. This approach allows for more specific PCR assessment of the lymphocytic infiltrate and for rapid DNA extraction and PCR analysis.

RESULTS

Using the LCM approach, we could demonstrate clonal T-cell receptor gamma gene rearrangements in biopsy specimens that did not show clonality using DNA extracted by conventional methods from full tissue sections. In addition, DNA extraction and PCR analysis can be performed in 11 h.

CONCLUSION

In conclusion, applying LCM to clonality analysis of cutaneous lymphocytic infiltrates is rapid and more sensitive than conventional methods, and we recommend introducing this approach into the routine diagnostic setting.

B-cell monoclonality is associated with lymphoid follicles in gastritis

The gold standard for diagnosis of gastric MALT lymphoma is histopathology. Polymerase chain reaction-based assays to detect the expansion of monoclonal B cells have also been used to corroborate the diagnosis. However, there are conflicting data on monoclonal B-cell expansion in gastritis. We asked about its frequency in graded gastritis cases. Lymphocytic infiltration in gastric biopsies was graded according to Wotherspoon in 129 cases. The histologic diagnosis ranged from normal gastric mucosa to suspicious for gastric MALT lymphoma. To search for a monoclonal B-cell population, a semi-nested polymerase chain reaction strategy was used for amplification of rearranged VDJ sequences of the immunoglobulin heavy chain gene. Of 106 evaluable samples, 18 were found to be monoclonal. The detection of a monoclonal B-cell population was strongly associated with the presence of lymphoid follicles. In cases with lymphoid follicles, detection of monoclonality was independent of Wotherspoon grading; there is no significant difference between cases being suspicious for lymphoma and those not. We found B-cell monoclonality to be a more frequent than expected finding in gastritis and to be strongly associated with the presence of lymphoid follicles; thus, its presence is of little significance in patient management.

Monoclonality in Helicobacter pylori-positive gastric biopsies: an early detection of mucosa-associated lymphoid tissue lymphoma

Mucosa-associated lymphoid tissue (MALT) is not present in healthy gastric mucosa, but it can develop in sites of long-persisting inflammation and is connected with the development of MALT lymphoma. A monoclonal lymphocyte population is one of the characteristics of such lymphomas. In this study we analyzed gastric biopsies (formalin fixed and paraffin embedded or frozen) in 93 patients with dyspepsia accompanied by Helicobacter pylori infection. We applied PCR and single-cell immunocytochemistry to detect the clonality of the gastric B-cell population. Immunocytochemistry performed on 33 frozen biopsies showed two samples with monoclonal pattern. PCR analysis of immunoglobulin heavy-chain (IgH) gene rearrangements revealed two monoclonal populations out of 161 biopsies from 60 patients. We conclude that PCR analysis was the most sensitive method, which gave us insight into the nature of the earliest stage of MALT lymphoma in gastric biopsies.

Immunoglobulin heavy chain gene analysis in lymphomas: a multi-center study demonstrating the heterogeneity of performance of polymerase chain reaction assays

Determination of monoclonality through an evaluation of immunoglobulin heavy chain (IgH) gene rearrangements is a commonly performed and useful diagnostic assay. Many laboratories that perform this assay do so by the polymerase chain reaction (PCR). To evaluate current methods for performing IgH gene testing, 19 different Association of Molecular Pathology (AMP) member laboratories analyzed 29 blinded B cell and T cell lymphoid neoplasm samples of extracted DNA and formalin-fixed, paraffin-embedded (FFPE) tissue and were asked to complete a technical questionnaire. From this study, it is clear that Southern blot analysis remains the diagnostic gold standard, with a 100% diagnostic sensitivity and specificity. There was, however, remarkable heterogeneity in the performance of, and results obtained from, IgH PCR assays with diagnostic sensitivity ranging from over 90% to as low as 20%, when evaluating the same specimens. Many laboratories overestimate the diagnostic sensitivity of their IgH PCR assay, and there was a significant, and under appreciated, drop-off (from 61.3% to 41.8%) in detection in paired FFPE as compared with fresh/frozen tissues. Fixation has a dramatic impact on the inability to perform the test on FFPE (43.1%) versus DNA already extracted from fresh or frozen tissue (2.8%). A number of variables that affected the outcome of IgH PCR were identified. Strategies that improved the detection of monoclonal IgH rearrangements include: the addition of FRII to the FRIII upstream primer (increasing detection from 57.3% to 73.6%) and the use of the FR3A rather than the FR3 FRIII primer (increasing detection from 54.7% to 69.7%). Although numerous variables (from DNA extraction to PCR product detection) were evaluated, making it difficult to mandate alterations in laboratory practice, these findings ought to prompt diagnostic molecular pathology laboratories to reevaluate their claims of sensitivity, as well as their methodologies. Both pathologists and surgeons need to ensure that not all submitted material is fixed, if there is adequate sample. Importantly, there is a need for greater standardization to reduce the unacceptably high false negative rate of this crucial diagnostic assay.

Molecular diagnostics in low-grade gastric marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type after Helicobacter pylori eradication therapy

The primary gastric lymphomas are extranodal non-Hodgkin's lymphomas that likely originate from the mucosa-associated lymphoid tissue (MALT). Data suggest that chronic infection with Helicobacter pylori (H pylori) is significantly associated with the pathogenesis of low-grade gastric MALT lymphomas. This is in keeping with the observation that many patients with early low-grade MALT lymphomas have complete remissions after H pylori eradication therapy. However, the stability of these remissions remains unclear and relapses have been reported. It can be difficult to distinguish between early malignant and benign disorders of the gastric mucosa. A polymerase chain reaction (PCR) assay can detect rearrangements of the variable region of immunoglobulin heavy chains. This assay can be used to distinguish the clonality of B lymphocytes and has been investigated as a test for differential diagnosis of MALT lymphomas. Monoclonality is observed in the majority of MALT-lymphoma samples at diagnosis but has been found in gastritis samples as well. Whether the presence of monoclonal B cells is associated with the risk of lymphoma progression remains unclear. As many as 50% of patients who have complete histologic remissions of MALT lymphoma after H pylori eradication therapy have persisting monoclonal bands in follow-up PCR monitoring. Although it is unclear as to whether monoclonality indicates the presence of minimal residual disease, patients who have persistent monoclonal bands during follow-up should be considered at risk for relapse. The PCR assay for rearrangements of the variable region of the immunoglobulin heavy-chain gene appears to be of low value in the diagnosis of B-cell malignancies but could provide a useful tool in the follow-up of patients who achieve remissions after H pylori eradication.