Application of BIOMED-2 clonality assays to formalin-fixed paraffin embedded follicular lymphoma specimens: Superior performance of the IGK assays compared to IGH for suboptimal specimens

Analysis of clonality in cutaneous B-cell lymphoma and B-cell pseudolymphoma using skin flow cytometry: Comparison of immunophenotyping and gene rearrangement studies

To identify clonal neoplastic cells in skin affected by B-cell lymphoma using skin flow cytometry (FCM) techniques, we investigated light-chain restriction using skin FCM with clonality assessed by polymerase chain reaction and light-chain restriction by in situ hybridization (ISH). We retrospectively analyzed 16 cases of B-cell lymphoma with cutaneous involvement: primary cutaneous diffuse large B-cell lymphoma, leg type (pcDLBCL-LT) (n = 7), DLBCL-not otherwise specified (DLBCL-NOS) (n = 6), primary cutaneous follicle center lymphoma (pcFCL) (n = 1), and follicular lymphoma (n = 2), as well as cutaneous B-cell pseudolymphoma (n = 9). Results of skin FCM light-chain restriction analyses were compared with immunoglobulin H (IgH) gene rearrangement and κ/λ ISH findings. Skin FCM detected light-chain restriction in 11 of 14 B-cell lymphoma patients but none of the B-cell pseudolymphoma patients. The sensitivity of skin FCM for distinguishing B-cell lymphoma and B-cell pseudolymphoma was 79%, and the specificity was 100%. Eleven of 13 B-cell lymphoma patients exhibited gene rearrangement (sensitivity 85%), whereas six of seven pseudolymphoma patients were negative (specificity 86%). ISH was positive in three of 16 B-cell lymphoma cases (sensitivity 19%) but none of the B-cell pseudolymphoma cases (specificity 100%). ISH sensitivity was 29% for pcDLBCL-LT, 17% for DLBCL-NOS, and 0% for pcFCL and follicular lymphoma. Skin FCM therefore appears to be more sensitive than ISH in detecting light-chain restriction in DLBCL and follicular lymphoma, and as sensitive as IgH gene rearrangement analysis in detecting clonality. Skin FCM is thus a promising diagnostic tool for identifying monoclonal neoplastic B-cell populations.

Evaluation of a worldwide EQA scheme for complex clonality analysis of clinical lymphoproliferative cases demonstrates a learning effect

Clonality analysis of immunoglobulin (IG) or T-cell receptor (TR) gene rearrangements is routine practice to assist diagnosis of lymphoid malignancies. Participation in external quality assessment (EQA) aids laboratories in identifying systematic shortcomings. The aim of this study was to evaluate laboratories' improvement in IG/TR analysis and interpretation during five EQA rounds between 2014 and 2018. Each year, participants received a total of five cases for IG and five cases for TR testing. Paper-based cases were included for analysis of the final molecular conclusion that should be interpreted based on the integration of the individual PCR results. Wet cases were distributed for analysis of their routine protocol as well as evaluation of the final molecular conclusion. In total, 94.9% (506/533) of wet tests and 97.9% (829/847) of paper tests were correctly analyzed for IG, and 96.8% (507/524) wet tests and 93.2% (765/821) paper tests were correctly analyzed for TR. Analysis scores significantly improved when laboratories participated to more EQA rounds (p=0.001). Overall performance was significantly lower (p=0.008) for non-EuroClonality laboratories (95% for IG and 93% for TR) compared to EuroClonality laboratories (99% for IG and 97% for TR). The difference was not related to the EQA scheme year, anatomic origin of the sample, or final clinical diagnosis. This evaluation showed that repeated EQA participation helps to reduce performance differences between laboratories (EuroClonality versus non-EuroClonality) and between sample types (paper versus wet). The difficulties in interpreting oligoclonal cases highlighted the need for continued education by meetings and EQA schemes.

[Clinicopathological analysis of mucosa associated lymphoid tissue lymphoma secondary to Sjögren' s syndrome in salivary gland]

OBJECTIVE

To analyze the clinicopathological characteristics of mucosa associated lymphoid tissue (MALT) lymphoma secondary to Sjögren' s syndrome (SS) (SS-MALT lymphoma) in salivary gland and to explore the value of the combined application of histopathological morphology, protein expression and molecular phenotype in pathological diagnosis and prognostic evaluation of SS-MALT lymphoma.

METHODS

Sixteen patients with SS-MALT lymphoma were collected from 260 patients who were diagnosed with SS in Peking University School and Hospital of Stomatology from January 1997 to December 2016. Twelve patients with non-MALT lymphoma secondary to SS (non-SS-MALT lymphoma) in salivary gland were selected as controls. The clinical data of the patients were retrospectively reviewed and analyzed. All the patients were followed up until December 20, 2019. Hematoxylin-eosin staining, immunohistochemistry, polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) techniques were used to observe the histologic characteristics and to detect the manifestations of light chain restrictive expression, immunoglobulin (Ig) gene clonal rearrangement, chromosome translocation and gene abnormality, so as to evaluate their values in pathological diagnosis and prognostic evaluation.

RESULTS

The malignant transformation rate of SS to MALT lymphoma was about 6.15%, ranged from 3 to 240 months, during which 2 patients died due to high-level deterioration. Microscopically, the acini of the glandular tissue were atrophied and destroyed. The tumor cells dominated by central cell-like lymphocytes grew diffusely, destroying the epithelial islands. All SS-MALT lymphoma cases were positive in CD20 and Pax5. Half of them had the Ki-67 proliferation index of 10% or less, and half greater than 10%. 93.75% cases expressed AE1/AE3 protein, which showed the residual glandular epithelium. All the tumor cells were negative in CD3ε, and the plasma cells were detected by CD138 antigen. The light chain restrictive expression of κ and λ was 37.5% in SS-MALT lymphoma group. The positive detection rates of immunoglobulin heavy chain (IgH)-FR1, IgH-FR2, IgH-FR3, immunoglobulin kappa chain (IgK)-A, and IgK-B in SS-MALT lymphoma group were 33.3%, 53.3%, 33.3%, 20.0%, and 26.7%, respectively, and 93.3% when together used with IgH and IgK. The positive rates of the MALT1, IGH and BCL6 genes with dual color break-apart probes were 36.4%, 27.3% and 27.3%, and the detection rate of chromosome translocation and gene abnormality by applying the three probes was 72.7%.

CONCLUSION

There are no specific histological characteristics and protein phenotypes in the histologic diagnosis of SS-MALT lymphoma in salivary gland. The combined application of histopathological manifestations, immunohistochemistry, PCR and FISH techniques helps the accurate pathologic diagnosis of the disease. Although SS-MALT lymphoma is considered as an indolent lymphoma with a relatively favorable prognosis, the regular return visit and long-term follow-up should be conducted to detect the clues of recurrence and advanced deterioration.

Next-generation sequencing of immunoglobulin gene rearrangements for clonality assessment: a technical feasibility study by EuroClonality-NGS

One of the hallmarks of B lymphoid malignancies is a B cell clone characterized by a unique footprint of clonal immunoglobulin (IG) gene rearrangements that serves as a diagnostic marker for clonality assessment. The EuroClonality/BIOMED-2 assay is currently the gold standard for analyzing IG heavy chain (IGH) and κ light chain (IGK) gene rearrangements of suspected B cell lymphomas. Here, the EuroClonality-NGS Working Group presents a multicentre technical feasibility study of a novel approach involving next-generation sequencing (NGS) of IGH and IGK loci rearrangements that is highly suitable for detecting IG gene rearrangements in frozen and formalin-fixed paraffin-embedded tissue specimens. By employing gene-specific primers for IGH and IGK amplifying smaller amplicon sizes in combination with deep sequencing technology, this NGS-based IG clonality analysis showed robust performance, even in DNA samples of suboptimal DNA integrity, and a high clinical sensitivity for the detection of clonal rearrangements. Bioinformatics analyses of the high-throughput sequencing data with ARResT/Interrogate, a platform developed within the EuroClonality-NGS Working Group, allowed accurate identification of clonotypes in both polyclonal cell populations and monoclonal lymphoproliferative disorders. This multicentre feasibility study is an important step towards implementation of NGS-based clonality assessment in clinical practice, which will eventually improve lymphoma diagnostics.

Metastatic intestinal adenocarcinoma to a lymph node involved by follicular lymphoma: The importance of looking beyond the apparent

Composite tumors consisting of follicular lymphoma (FL) and colorectal or small intestinal adenocarcinoma are exceedingly rare, with only four cases published in the literature, to the best of our knowledge. While in most of these cases the clinical prognosis seems to be determined by the adenocarcinoma, at least one patient has shown rapid and aggressive progression of the FL. Here we report on a 62 year-old male with colonic adenocarcinoma metastatic to a retroperitoneal lymph node involved by FL, which illustrates the importance of carefully examining the histomorphology of lymphoid elements in surgical specimens.

Evaluation diagnostic usefulness of immunoglobulin light chains (Igκ, Igλ) and incomplete IGH D-J clonal gene rearrangements in patients with B-cell non-Hodgkin lymphomas using BIOMED-2 protocol

PURPOSE

Evaluation diagnostic usefulness of immunoglobulin light chains (Igκ, Igλ) and incomplete IGH D-J clonal gene rearrangements in formalin-fixed, paraffin-embedded (FFPE) tissue of patients with B-cell non-Hodgkin lymphomas (B-NHL).

MATERIALS AND METHODS

This study was performed on samples from 70 patients with B-NHL, including two cases of follicular lymphoma (FL), 20 cases of diffuse large B-cell lymphoma (DLBCL), one case of mantle cell lymphoma (MCL), and 47 cases of B-cell neoplasm (non-classified), which had been previously assessed for complete IGH clonality, and failure to clarify gene rearrangements. We used a gold standard multiplex PCR protocol provided by European Biomedicine and Health (BIOMED-2) Concerted Action Project BMH4-CT98-3936 for improvement of diagnosis and analysis of clonality gene rearrangement in lymphoma malignancies.

RESULTS

Our results revealed a total positive monoclonality of 89 % (62/70) in Igκ, Igλ, and 11.4 % (8/70) polyclonality in gene rearrangements assay. The samples with positive clonality consisting (Igκ: 45 %, Igλ: 55 %) in DLBCL, (Igκ: 100 %) in FL, (Igλ: 100 %) in MCL, and (Igκ: 47 %, Igλ: 36 %) in B-cell neoplasm non-classified. None of the incomplete IGH D-J immunoglobulin gene families (0 %) showed monoclonality, and all samples demonstrated polyclonality pattern.

CONCLUSIONS

Our findings on FFPE tissue revealed that immunoglobulin light chains clonality gene rearrangements assays using BIOMED-2 protocol, could be considered a valuable and reliable method for clonality detection, particularly in cases of failure of complete IGH gene rearrangements analysis. Clonal Ig gene rearrangements assay is applicable for routine diagnostic testing of lymphoproliferative disorders and as a reliable method for differentiating between malignant and benign lymphoma disorders.

The evolution of clonality testing in the diagnosis and monitoring of hematological malignancies

Currently, distinguishing between benign and malignant lymphoid proliferations is based on a combination of clinical characteristics, cyto/histomorphology, immunophenotype and the identification of well-defined chromosomal aberrations. However, such diagnoses remain challenging in 10-15% of cases of lymphoproliferative disorders, and clonality assessments are often required to confirm diagnostic suspicions. In recent years, the development of new techniques for clonality detection has allowed researchers to better characterize, classify and monitor hematological neoplasms. In the past, clonality was primarily studied by performing Southern blotting analyses to characterize rearrangements in segments of the IG and TCR genes. Currently, the most commonly used method in the clinical molecular diagnostic laboratory is polymerase chain reaction (PCR), which is an extremely sensitive technique for detecting nucleic acids. This technique is rapid, accurate, specific, and sensitive, and it can be used to analyze small biopsies as well as formalin-fixed paraffin-embedded samples. These advantages make PCR-based approaches the current gold standard for IG/TCR clonality testing. Since the completion of the first human genome sequence, there has been a rapid development of technologies to facilitate high-throughput sequencing of DNA. These techniques have been applied to the deep characterization and classification of various diseases, patient stratification, and the monitoring of minimal residual disease. Furthermore, these novel approaches have the potential to significantly improve the sensitivity and cost of clonality assays and post-treatment monitoring of B- and T-cell malignancies. However, more studies will be required to demonstrate the utility, sensitivity, and benefits of these methods in order to warrant their adoption into clinical practice. In this review, recent developments in clonality testing are examined with an emphasis on highly sensitive systems for improving diagnostic workups and minimal residual disease assessments.

Clonality testing of malignant lymphomas with the BIOMED-2 primers in a large cohort of 1969 primary and consultant biopsies

The introduction of the BIOMED-2 primers allowed for reliable comparisons of clonality testing data of malignant lymphomas from different laboratories. This study undertook a retrospective analysis of a large cohort of cases; 1862 cases involved the immunoglobulin heavy chain locus (IGH VH-JH), and 1527 cases involved the T cell receptor gamma locus (TCRG). We confirmed previously published clonality rates in various B cell, T cell, and Hodgkin lymphoma cases. In reactive lesions, clonality for the IGH locus was frequently accompanied by additional polyclonal background. Clonality for TCRG was found in a subgroup of diffuse large B cell lymphomas. On closer morphologic inspection, seven cases appeared to have arisen from an underlying peripheral T-cell lymphoma. Five cases with monoclonal TCRG rearrangements, originally diagnosed as Hodgkin lymphomas, were reclassified as T-cell lymphomas. TCRG clonality was very rarely only observed in Hodgkin lymphoma. In case of clear TCRG clonality a T-cell neoplasia must be ruled out on morphological grounds. By careful examination of the rearrangement patterns, including an assessment of a co-amplified polyclonal background, clonality testing provides a powerful tool which in concert with morphologic and immunohistochemical parameters can lead to a firm diagnosis.

Molecular Pathology of Malignant Lymphoma

This review focuses on practical uses of molecular testing in mature B-cell and T-cell lymphomas with a focus on those lymphomas in which molecular testing is common. Clinical findings, histology, and biomarkers, as well as diagnostic and prognostic predictive value and practical applications of molecular testing for mature B- and T-cell lymphomas are presented.

EuroClonality/BIOMED-2 guidelines for interpretation and reporting of Ig/TCR clonality testing in suspected lymphoproliferations

PCR-based immunoglobulin (Ig)/T-cell receptor (TCR) clonality testing in suspected lymphoproliferations has largely been standardized and has consequently become technically feasible in a routine diagnostic setting. Standardization of the pre-analytical and post-analytical phases is now essential to prevent misinterpretation and incorrect conclusions derived from clonality data. As clonality testing is not a quantitative assay, but rather concerns recognition of molecular patterns, guidelines for reliable interpretation and reporting are mandatory. Here, the EuroClonality (BIOMED-2) consortium summarizes important pre- and post-analytical aspects of clonality testing, provides guidelines for interpretation of clonality testing results, and presents a uniform way to report the results of the Ig/TCR assays. Starting from an immunobiological concept, two levels to report Ig/TCR profiles are discerned: the technical description of individual (multiplex) PCR reactions and the overall molecular conclusion for B and T cells. Collectively, the EuroClonality (BIOMED-2) guidelines and consensus reporting system should help to improve the general performance level of clonality assessment and interpretation, which will directly impact on routine clinical management (standardized best-practice) in patients with suspected lymphoproliferations.

B Cells Behaving Badly: A Better Basis to Behold Belligerence in B-Cell Lymphomas

A plethora of genetic abnormalities has been described in B-cell lymphomas, some of which arise when physiologic mechanisms involved in the generation of immunologic diversity go awry. Several different lymphoma types, such as follicular lymphoma (FL), mantle cell lymphoma (MCL), and Burkitt lymphoma (BL), are associated with hallmark translocations that occur as a consequence of these errors (t(14;18)(q32;q21), t(11;14)(q13;q32), and t(8;14)(q24;q32), respectively); however, none of these associations is absolute and none is completely diagnostically specific or sensitive. The advantages and limitations of a variety of different testing strategies in the 2 most common lymphomas, FL and diffuse large B-cell lymphoma (DLBCL), are reviewed herein, including an evaluation of the role of PCR-based approaches, FISH, and more nascent genomic technologies. The use of immunophenotypic strategies that may potentially provide, albeit imperfectly, more user-friendly surrogates for underlying genetic aberrations and cell-of-origin designations derived from gene-expression profiling analyses are also discussed. Finally, a newly designated category of lymphoma with features intermediate between DLBCL and BL is appraised, highlighting the central role of genetic analysis in this diagnostic gray zone.

A parallel comparison of T-cell clonality assessment between an in-house PCR assay and the BIOMED-2 assay leading to an efficient and cost-effective strategy

AIMS

Diagnosis of T-cell lymphoproliferation is sometimes challenging, and in certain instances pathologists rely heavily on the clonality assessment results of T-cell receptor (TCR) gene rearrangement (TCR-GR). Many investigators have designed various in-house primer sets for PCR-based study targeting different loci of TCR genes. In recent years, the commercial BIOMED-2 protocols have become available. The in-house primers are very cheap while the BIOMED-2 primers are expensive. This parallel study aimed to compare the sensitivity of the in-house TCRG primers (two reactions) and the BIOMED-2 TCR primers (six reactions) in an attempt to develop a sensitive and cost-effective strategy for TCR-GR assessment.

METHODS

PCR-based analysis was performed on 69 samples of T-lineage neoplasms including 60 formalin-fixed paraffin-embedded (FFPE) tissues, 5 samples from peripheral blood (PB) and 4 samples from bone marrow (BM) aspirate.

RESULTS

Forty-seven (78%) FFPE and all PB or BM aspirate samples yielded control DNA products suitable for clonality assessment including 4 precursor and 50 mature T-cell neoplasms. The detection rates of clonal TCR-GR were 63% (34/54) by the two in-house TCRG primers, 85% (46/54) by all six BIOMED-2 reactions, 91% (49/54) by combining the in-house and BIOMED-2 TCRG reactions and 94% (51/54) by combining the in-house and all BIOMED-2 reactions. By using the in-house and BIOMED-2 TCRG reactions with a total of four tubes, clonal TCR-GR was detected in 91% of the cases. The reagent cost for this combination was one-third of that for the six BIOMED-2 reactions and the detection rate was also higher than the latter alone (91% vs 85%).

CONCLUSIONS

As the in-house primers were custom made and are much cheaper than the commercial kits, the authors concluded that this four-tube strategy was cost-effective and efficient for TCR-GR clonality assessment.

The value of molecular diagnostics in primary cutaneous B-cell lymphomas in the context of clinical findings, histology, and immunohistochemistry

BACKGROUND

Primary cutaneous B-cell lymphoma (PCBCL) is classified into 3 major subtypes: primary cutaneous follicle center lymphoma (PCFCL); primary cutaneous marginal zone B-cell lymphoma (PCMZL); and primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL, LT). Diagnosis of PCBCL is mainly based on clinical and (immuno)-histochemical grounds.

OBJECTIVE

We investigated the diagnostic value of the BIOMED-2 Concerted Action BMH4 CT98-3936 protocol in PCBCL.

METHODS

We analyzed with the BIOMED-2 Concerted Action BMH4 CT98-3936 protocol skin specimens from patients with well-defined clinical and (immuno)-histologic PCBCL (n = 18) in comparison with benign lymphocytic infiltrates (n = 9). For molecular staging we also investigated 13 extracutaneous samples from 6 patients with PCLBCL, LT. Each sample was investigated at least twice.

RESULTS

Monoclonality was detected in all of 5 PCFCL; 5 of 6 PCMZL; all of 6 PCLBCL, LT; and 2 of 9 benign lymphocytic infiltrates. In 5 of 6 patients with PCLBCL, LT, a clone corresponding to the clone detected in the skin was detected in 3 of 5 bone-marrow, 4 of 5 blood, and 1 of 3 lymph node specimens. DNA amplification using tubes A and B of IgH was not possible in PCFCL/PCMZL, benign lymphocytic infiltrates, and extracutaneous specimens of PCLBCL, LT, even after repeated analysis up to 11 times. Pseudomonoclonality was identified by repeated analyses in one case of PCMZL and in one case of benign lymphocytic infiltrate.

LIMITATIONS

A multicentric, randomized, blinded study is necessary to confirm our results.

CONCLUSION

Molecular diagnosis supports the clinical and (immuno)-histologic diagnosis in PCBCL. In PCLBCL, LT, molecular staging may be useful. Tubes C through E of IgH and Igκ analyses seem to be superior to tubes A and B of IgH. Each sample should be analyzed at least twice to assess the possibility of pseudomonoclonality.

The basis and rational use of molecular genetic testing in mature B-cell lymphomas

An increasing number of neoplasms are associated with variably specific genetic abnormalities. This is best exemplified by hematological malignancies, in which there is a growing list of entities that are defined by their genetic lesion(s); this is not (yet) the case in mature B-cell lymphomas. However, enhanced insights into the pathogenesis of this large and diverse group of lymphomas have emerged with the ongoing unraveling of a plethora of fascinating genetic abnormalities. The purpose of this review is to synthesize well-recognized data and nascent discoveries in our understanding of the genetic basis of a spectrum of mature B-cell lymphomas, and how this may be applied to contemporary clinical practice. Despite the explosion of new and exciting knowledge in this arena, with the potential for enhanced diagnostic and prognostic strategies, it is essential to remain cognizant of the limitations (and complexity) of genetic investigations, so that assays can be developed and used both judiciously and rationally.

PCR assays detect B-lymphocyte clonality in formalin-fixed, paraffin-embedded specimens of classical hodgkin lymphoma without microdissection

Hodgkin lymphoma (HL) was shown to be a B-cell malignancy using polymerase chain reaction (PCR) clonality studies of microdissected Reed-Sternberg cells. While methods for the detection of B-cell clonality could aid in the diagnosis of HL, microdissection is not practical in most clinical settings. We assessed the standardized BIOMED-2 IGH and IGK PCR primers for the detection of clonality using 50 consecutively diagnosed formalin-fixed, paraffin-embedded (FFPE) classic HL specimens. Without microdissection, clonality was detected in 23 of 47 assessable cases. The IGK assay was significantly more sensitive than the IGH assay (18 vs 10 positive results). These data and 2 representative cases demonstrate that PCR-based B-cell clonality assays have usefulness when the histologic differential diagnosis of an FFPE specimen includes classic HL.

Expanded and highly active proliferation centers identify a histological subtype of chronic lymphocytic leukemia ("accelerated" chronic lymphocytic leukemia) with aggressive clinical behavior

BACKGROUND

The concept of "accelerated" chronic lymphocytic leukemia is frequently used by both pathologists and clinicians. However, neither histological criteria to define this form of chronic lymphocytic leukemia nor its clinical correlates and prognostic impact have been formally defined in large series of patients.

DESIGN AND METHODS

Tissue biopsies from 100 patients with chronic lymphocytic leukemia were analyzed for the size of proliferation centers and their proliferation rate as assessed by mitosis count and Ki-67 immunostaining. Histological patterns were correlated with main clinico-biological features and outcome.

RESULTS

A suspicion of disease transformation was the main reason for carrying out tissue biopsy, which was performed at a median time of 14 months (range, 0 to 204 months) after the diagnosis of chronic lymphocytic leukemia. The biopsy showed histological transformation to diffuse large B-cell lymphoma in 22 cases. In the remaining 78 patients, the presence of expanded proliferation centers (broader than a 20x field) and high proliferation rate (either >2.4 mitoses/proliferation center or Ki-67 >40%/proliferation center) predicted a poor outcome and were selected to define a highly proliferative group. Thus, 23 patients with either expanded proliferation centers or high proliferation rate were considered as having "accelerated" chronic lymphocytic leukemia. These patients displayed particular features, including higher serum lactate dehydrogenase levels and more frequently elevated ZAP-70 than "non-accelerated" cases. The median survival from biopsy of patients with "non-accelerated" chronic lymphocytic leukemia, "accelerated" chronic lymphocytic leukemia and transformation to diffuse large B-cell leukemia was 76, 34, and 4.3 months, respectively (P<0.001).

CONCLUSIONS

The presence of expanded and/or highly active proliferation centers identifies a group of patients with "accelerated" chronic lymphocytic leukemia characterized by an aggressive clinical behavior.

PCR clonality detection in Hodgkin lymphoma

B-cell clonality detection in whole tissue is considered indicative of B-cell non-Hodgkin lymphoma (NHL). We tested frozen tissue of 24 classical Hodgkin lymphomas (cHL) with a varying tumor cell load with the multiplex polymerase chain reaction (PCR) primer sets for IGH and IGK gene rearrangement (BIOMED-2). A clonal population was found in 13 cases with the IGH FR1 and/or FR2/FR3 PCRs. Using the IGK-VJ and IGK-DE PCRs, an additional six cases had a dominant clonal cell population, resulting in a detection rate of 79% in frozen tissue. Of 12 cases, also the formalin-fixed and paraffin-embedded (FFPE) tissue was tested. Surprisingly, in eight of the 12 FFPE cases with acceptable DNA quality (allowing PCR amplification of >200 nt fragments), the IGK multiplex PCRs performed better in detecting clonality (six out of eight clonal IGK rearrangements) than the IGH PCRs (four out of nine clonal rearrangements), despite a rather large amplicon size. There was no evidence of B-cell lymphoma during follow-up of 1 to 6 years and no correlation was found between the presence of a clonal result and Epstein-Barr virus in the tumor cells. Our results indicate that the present routine PCR methods are sensitive enough to detect small numbers of malignant cells in cHL. Therefore, the presence of a clonal B-cell population does not differentiate between cHL and NHL.

Pitfalls in TCR gene clonality testing: teaching cases

Clonality testing in T-lymphoproliferations has technically become relatively easy to perform in routine laboratories using standardized multiplex polymerase chain reaction protocols for T-cell receptor (TCR) gene analysis as developed by the BIOMED-2 Concerted Action BMH4-CT98-3936. Expertise with clonality diagnostics and knowledge about the biology of TCR gene recombination are essential for correct interpretation of TCR clonality data. Several immunobiological and technical pitfalls that should be taken into account to avoid misinterpretation of data are addressed in this report. Furthermore, we discuss the need to integrate the molecular data with those from immunohistology, and preferably also flow cytometric immunophenotyping, for appropriate interpretation. Such an interactive, multidisciplinary diagnostic model guarantees integration of available data to reach the most reliable diagnosis.

Malleable immunoglobulin genes and hematopathology - the good, the bad, and the ugly: a paper from the 2007 William Beaumont hospital symposium on molecular pathology

Immunoglobulin gene rearrangement analysis is one of the more commonly performed assays available on the hematopathology menu of clinical molecular pathology laboratories. The analysis of these rearrangements provides useful information on a number of different levels in the evaluation of lymphoproliferations. An appreciation of the various mechanisms involved in the numerous physiological pathways affecting the immunoglobulin genes, and hence antibody molecules, is central to an understanding of B-cell development vis-à-vis the generation of immunological diversity. Knowledge about the intricate complexities of these mechanisms is also germane to an evaluation of testing methodologies. With this information, it is easier to develop an understanding of how contemporary molecular testing of immunoglobulin gene rearrangements has evolved, from historically quite heterogeneous, fairly flawed, and rather ugly approaches to current more-standardized protocols. In addition, recognition of how such genetic changes with good intentions can turn bad has fostered increasing insights into the pathogenesis of B-cell lymphomas and leukemias. Despite the significant improvements in the design of immunoglobulin gene rearrangement assays, numerous pitfalls and caveats remain. Accordingly, it is crucial to consider such testing a tool, and although most useful, it is one of many tools that may be required to build cogent diagnoses.

Quantifying the role of aberrant somatic hypermutation in transformation of follicular lymphoma

Somatic hypermutation (SHM) aberrantly targets proto-oncogenes in various non-Hodgkin's lymphoma. To test the association of SHM with transformation of follicular lymphoma (FL), we sequenced mutational hot spots in five proto-oncogenes (BCL6, PAX5, RHOH, MYC and PIM1) in 32 low-grade FL (lgFL) with follicular histology and 26 transformed FL (tFL) with diffuse large cell histology. No difference was detected in the fraction of specimens mutated (75% of lgFL and 77% of tFL) or in the mutation load (0.08 for lgFL vs. 0.06 mutations/100 bp/allele for tFL). Serial specimens were examined from 25 patients showing stable low-grade FL (slgFL; n=6) or a low-grade FL that later transformed into diffuse large cell lymphoma (tFL; n=19). slgFL and tFL patients accumulated similar numbers of mutations in the interval between biopsies. These data indicate that mutations attributable to aberrant SHM occur with similar frequency in low-grade and transformed FL; transformation is not associated with a higher rate of aberrant SHM. Moreover, the frequency of mutations attributable to aberrant SHM in tFL was significantly lower than that reported for de novo diffuse large B cell lymphoma, suggesting differing oncogenic mechanisms in transformed follicular lymphoma and de novo diffuse large B cell lymphoma.