B-cell gene rearrangement in benign and malignant lymphoid proliferations of mucosa-associated lymphoid tissue and lymph nodes

Two cases of gastric mucosa-associated lymphoid tissue (MALT) lymphoma masquerading as follicular gastritis

In this report, we describe two cases of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) of the stomach, which presented with multiple small, whitish nodules in the gastric body. The endoscopic appearance was similar to that of lymphoid follicular hyperplasia found in follicular gastritis or nodular gastritis. Both patients were positive for Helicobacter pylori, and the eradication treatment resulted in complete remission of the lymphoma. However, recurrence was noted in one patient. These cases indicate that, although infrequent, gastric MALT lymphoma can show a nodular appearance resembling that of follicular gastritis.

Primary T-cell lymphoma of the thyroid associated with Hashimoto's thyroiditis, histologically mimicking MALT-lymphoma

Most of thyroid lymphomas are B-lineage, and T-cell lymphomas are rare. Here, we report a case of primary thyroid T-cell lymphoma associated with Hashimoto's thyroiditis. A 48-yr-old woman presented with incidentally found neck mass. Histologically, the resected right lobe of the thyroid was replaced by monomorphic small atypical lymphoid cells with lymphoepithelial lesion-like change, most of which were immunoreactive for CD3, CD8, betaF-1, and TIA-1. Peripheral T-cell lymphoma, unspecified, was finally diagnosed after molecular study for TCR-gamma gene rearrangement. This is the second case of cytotoxic T-cell lymphoma reported in the thyroid gland so far. Unique association between thyroid follicles and neoplastic lymphocytes may be characteristic feature of this type of T-cell lymphoma.

Florid reactive lymphoid hyperplasia of the lower female genital tract (lymphoma-like lesion): a benign condition that frequently harbors clonal immunoglobulin heavy chain gene rearrangements

Lymphoma-like lesions (LLL) of the lower female genital tract are florid reactive inflammatory processes that mainly occur in women in their reproductive years. Histologically, they are characterized by a dense lymphoid infiltrate with admixed large cells that is often suspicious for lymphoma. In contrast to lymphoma, however, they are superficial lesions that typically show surface erosion and a mixed lymphoid infiltrate and do not have evidence of a mass, deep invasion, or prominent sclerosis. With the advent of widespread molecular genetic testing, it would seem that LLLs should be polyclonal helping make the correct diagnosis. However, we have found cases with morphologic and immunophenotypic features of LLLs and evidence of clonal rearrangement of the immunoglobulin heavy chain (IGH) gene, potentially leading to misdiagnosis. We examined the clinicopathologic features and outcome of 12 patients with LLL (9 in the cervix and 3 in the endometrium). The patients ranged in age from 18 to 54 (median 37) years and came to medical attention because of squamous dysplasia (8 patients), vaginal bleeding (3), or adnexal mass (1). One patient had an endocervical polyp, but otherwise none had a discrete mass. The specimens contained a dense, polymorphous inflammatory infiltrate, commonly associated with mucosal erosion. Immunohistochemical studies showed a mixture of B and T cells without immunoglobulin light chain restriction. Four cases (all cervical) had a clonal IGH gene rearrangement by PCR. There was no evidence of lymphoma on staging or on follow-up in any patient, including the 4 patients with clonal IGH rearrangement, after a mean follow-up of 3.5 years (range: 4 mo to 13 y). In summary, we describe 12 patients with LLL of the lower female genital tract. Four of the 9 cases (44%) analyzed by PCR had a clonal IGH gene rearrangement. The clinical and pathologic features of these cases suggest that a clonal IGH rearrangement in this setting does not warrant a diagnosis of lymphoma. Careful correlation of clinical, histologic, immunophenotypic, and genetic features is required to avoid misdiagnosis and inappropriate treatment. Routine microscopic findings and detailed clinical information remain paramount in establishing the correct diagnosis.

Analysis of T-cell clonality using laser capture microdissection and high-resolution microcapillary electrophoresis

Identification of clonal lymphocytic populations by polymerase chain reaction may be difficult in cases with scant cellular infiltrates or those with a heterogeneous population of cells. Here, we assessed the diagnostic utility of laser capture microdissection (LCM) and high-resolution microcapillary electrophoresis in the analysis of clonality of small biopsy specimens. Clonality was determined in 24 cases: five reactive tonsils, five reactive lymph nodes, six inflammatory skin lesions, and eight T-cell lymphomas. CD3-positive T lymphocytes were captured by LCM from paraffinized immunohistochemically stained sections. Genomic DNA was analyzed for T-cell receptor-gamma gene rearrangement by polymerase chain reaction followed by high-resolution microcapillary electrophoresis with the DNA 500 LabChip and the Agilent Bioanalyzer. In the reactive specimens, T-cell receptor-gamma polymerase chain reaction revealed monoclonal bands when 10 to 1000 cells were captured. This pattern changed to polyclonal when higher numbers of cells were microdissected (2000 to 10,000 cells). In contrast, lymphoma cells were consistently monoclonal whether low or high numbers were microdissected. Microcapillary electrophoresis coupled with LCM facilitated clonality analysis in equivocal cases. In two of eight lymphoma cases, LCM revealed diagnostic monoclonal bands, whereas routine T-cell receptor-gamma assessment of whole tissue sections with 10% polyacrylamide gel electrophoresis demonstrated only minor clonal bands. We conclude that clonality determined by LCM is cell number-dependent. Biopsy specimens containing low numbers of reactive polyclonal T cells may produce pseudomonoclonal bands and therefore should be interpreted with great caution.

Crystalline plasma cell inclusions in helicobacter-associated gastritis

BACKGROUND

Crystalline cytoplasmic inclusions are well documented in B cell lymphomas but have rarely been described in reactive plasmacytic infiltrates.

AIM

Three cases of Lelicobacter-associated gastritis are described in which plasma cells focally contained rhomboid and needle-shaped crystalline inclusions.

METHODS

Crystalline inclusions were identified in the gastric biopsy specimens from three patients undergoing routine upper gastrointestinal endoscopy. The cells were characterised immunohistochemically using the following antisera: cytokeratin, leucocyte common antigen, desmin, CD20, CD68, CD79a, CD138, immunoglobulin (Ig)G, IgA and IgM heavy chains, and kappa and lambda Ig light chains. Clinical follow-up data were obtained.

RESULTS

All biopsies showed a Lelicobacter-associated active chronic gastritis. Variable numbers of plasma cells with intracytoplasmic crystalline inclusions in the superficial lamina propria were seen. The crystals were not stained with any of the antisera tested, but the cells containing the crystals expressed CD79a and CD138 and, in the two assessable cases, showed IgA and lambda light chain immunoreactivity. The more numerous morphologically normal plasma cells in each patient were polytypic, and there were no histological features to suggest lymphoma. Crystals were not identified in the plasma cells in mucosal biopsy specimens from other sites in any of the patients.

CONCLUSIONS

Crystalline inclusions in plasma cells can occur in association with Lelicobacter gastritis. Although light chain restriction was shown in two patients, the overall histological and clinical findings indicated a reactive process. The presence of plasma cell crystals in isolation should not be considered to be diagnostic of lymphoma.

Clonality analyses in gastric MALT (mucosa-associated lymphoid tissue)

B-cell clonality, assessed by PCR for amplification of the VDJ region of the immunoglobulin heavy chain gene (IgH), is used to support the diagnosis of gastric mucosa-associated lymphoid tissue (MALT) lymphoma (GML). It has also been described in simple gastritis cases, without any histological hint for lymphoma, especially in the presence of lymphoid follicles. We analyzed a randomly selected series of 130 gastric biopsies with histologically described lymphoid follicle formation and investigated these for the prevalence of B-cell clonality using different PCR-based methods to discuss its usefulness in the differential diagnosis of GML. A seminested PCR for the IgH gene was performed and evaluated by agarose gel electrophoresis, GeneScan technique, and melting-curve analysis. The majority of cases revealed histologically chronic active Helicobacter pylori gastritis. Monoclonality was detected in 7.5% (10 of 130) and 7% (9 of 130) of samples using GeneScan technique and melting-curve analysis, respectively. In eight of eight samples investigated, monoclonality was not demonstrated in deeper sections of the same biopsy using GeneScan technique, favoring the diagnosis of a reactive process rather than overt lymphoma. Electrophoresis proved more difficult to interpret and revealed clonal cases in 14% (18 of 130). We conclude that GeneScan technique and melting curve analysis are the methods of choice for clonality analysis in gastric biopsies. Analyses of different deep sections with advanced PCR technology might be the method of choice for future analyses. In our opinion, the question of whether detected monoclonality can be interpreted as malignant lymphoma is still open.

Instability of clonality in gastric lymphoid infiltrates: a study with emphasis on serial biopsies

The evolution of low-grade B-cell mucosa-associated lymphoid-tissue (MALT) lymphoma of the stomach is a multistage process, reflected in the histologic continuum from Helicobacter pylori-chronic gastritis, to low-grade and high-grade lymphoma. Interestingly, in daily gastric biopsy sign-out, the authors observed that some biopsies showed monoclonality on polymerase chain reaction (PCR) even though there were no definite histologic features of malignancy and vice versa. To address the question, the authors studied the endoscopic gastric biopsies at first presentation of 46 patients to examine any clonality differences among various histologic patterns within the spectrum of MALT lymphoma evolution. The gastric biopsies were reviewed histologically and graded according to the Wotherspoon-Isaacson histologic scoring system from grade 0 (normal) to grade 5 (MALT lymphoma). The clonality of cases in each grade was determined by performing nested PCR for immunoglobulin heavy chain (IgH) gene rearrangement using FR2/JH and FR3/JH primer sets. The monoclonality rates among different grades were as follows: grade 2, 6.3% (1 of 16); grade 3, 27.3% (3 of 11); grade 4, 83.3% (5 of 6); grade 5, 69.2% (9 of 13). Statistically significant difference of monoclonality rate is demonstrated in histologic grade 4 versus grades 2 and 3, and grade 5 versus grade 2 (P < 0.05, Fisher exact test). The authors went on to examine the progress of disease by following up the clinical status, histologic changes, and clonality fluctuation of these cases. Four of the 8 patients with monoclonality on PCR, but no definite lymphoma at first presentation later progressed to frank MALT lymphoma. Our study shows that, during the progression to MALT lymphoma, there is an instability of clonality. Clonality can fluctuate between polyclonality, oligoclonality, and monoclonality, none of which defines an irreversible stage for progression to MALT lymphoma. Monoclonality is a risk factor for development of MALT lymphoma. Those cases with dense gastric mucosal lymphoid infiltrate (without definite MALT lymphoma) and monoclonality on PCR need to be closely monitored and Helicobacter infection promptly treated if present. In combination with clinicohistologic examination, PCR can serve as a complementary tool in arriving at a definite diagnosis of MALT lymphoma in cases with borderline histologic features.

An alternative protocol for DNA extraction from formalin fixed and paraffin wax embedded tissue

BACKGROUND

DNA extraction from paraffin wax embedded tissue requires special protocols, and most described methods report an amplification success rate of 60-80%.

AIMS

To propose a simple and inexpensive protocol consisting of xylene/ethanol dewaxing, followed by a kit based extraction.

METHOD

Xylene/ethanol dewaxing was followed by a long rehydration step and a kit based DNA extraction step.

RESULTS

This method produced a 100% amplification success rate for fragments of 121 to 227 bp for tamponated formalin fixed paraffin wax embedded tissue.

CONCLUSION

This cost effective and non-laborious protocol can successfully extract DNA from tamponated formalin fixed paraffin wax embedded tissue and should facilitate the molecular analysis of a large number of archival specimens in retrospective studies.

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.

Primary Pulmonary Lymphoma: Diagnosis and Follow-Up of 6 Cases and Review of an Uncommon Entity

Aims and background

Primary pulmonary lymphoma is an uncommon disease with a poorly defined management. We reviewed and followed the cases of primary pulmonary lymphoma in our institution to gather an estimation of this entity in our population.

Design and methods

We reviewed the records of all patients with biopsy-proven lymphoma of the lung. The main diagnostic criterion for primary pulmonary lymphoma was the absence of extrapulmonary involvement.

Results

We identified 6 cases of primary pulmonary lymphoma among 33 patients with biopsy-proven lymphoma of the lung evaluated in our center in a 12-year period. A radiological abnormality in an asymptomatic patient was the most common clinical presentation. Four cases were low-grade and two cases high-grade non-Hodgkin PPL. Histopathologic analyses of lung specimens obtained by transbronchial biopsy were sufficient for a diagnosis in 5 of the 6 cases and avoided invasive surgical maneuvers. Most patients followed an indolent course, but with a tendency to relapse.

Conclusions

Although clinical management of this entity is undefined, we feel bronchoscopic study, which is less aggressive than surgery, may be an adequate procedure for a diagnosis. Mono-chemotherapy using alkylating agents and careful clinical observation may be the best therapeutic approach for these patients, since most of them have favorable outcomes, whatever the treatment modalities.

Increased incidence of monoclonal B-cell infiltrate in chronic myeloproliferative disorders

A total of 106 trephine biopsy specimens with clinical, laboratory and pathology findings corresponding to chronic myeloproliferative disorders (CMPD) were analyzed to reveal the nature of the lymphoid infiltrate in the bone marrow. Histological investigation in 31 chronic myeloid leukemia (CML), 29 CMPDs not otherwise specified (CMPD-NOS), 28 essential thrombocytosis (ET), 15 polycythemia vera (PV) and three chronic eosinophilic leukemia/hypereosinophilic syndrome (CEL/HES) exhibited in 32% various amounts of lymphocytic infiltrate of sparsely to moderately diffuse or nodular types in the bone marrow, but the reactive or coinciding lymphomatous nature could not be revealed by histology alone in the majority of cases. PCR analysis of the immunoglobulin heavy chain (IgH) gene rearrangement was successfully performed in 81 out of the 106 DNA specimens extracted from formol-paraffin blocks. Out of the 81 samples with good-quality DNA, 18 gave a single or double discrete amplification band(s), which was reproducible only in four specimens. Sequencing finally proved monoclonal B-cell population of both pre- and postfollicular origin in all four samples (5%), one CML and three CMPD-NOS. Detailed clinical and pathological investigations indicated overt B-cell malignant lymphoma with clonal relationship to the CMPD in two out of these four patients. We conclude that detailed molecular analysis of IgH gene rearrangement in bone marrow samples of CMPD patients is needed to identify the true monoclonal B-cell infiltration, which-even without overt malignant lymphoma-may occur in this group of disorders. Modern Pathology (2004) 17, 1521-1530, advance online publication, 16 July 2004; doi:10.1038/modpathol.3800225.

Clonal B cell populations in a minority of patients with Hashimoto's thyroiditis

BACKGROUND

Hashimoto's thyroiditis (HT) is a risk factor for thyroid lymphoma, and clonal B cell populations in HT support this link. The literature on B cell clonality in HT is controversial.

AIMS

To identify clonal B cell populations in HT and to assess their usefulness in differentiating HT from mucosa associated lymphoid tissue (MALT) lymphoma and predicting future development of lymphoma.

METHODS

DNA from formalin fixed, paraffin wax embedded blocks of thyroid specimens from 10 patients with HT and two thyroid MALT lymphomas was analysed for B cell clonality by seminested polymerase chain reaction (PCR) using FRIII/LJH and FRIII/VLJH primers to amplify the IgH gene VDJ region. In one case, PCR products were sequenced. Immunohistochemistry was performed by labelled streptavidin-biotin technique using antibodies to: CD45, CD45RO, CD3, CD20, and cytokeratin.

RESULTS

The histopathological and clinical findings were characteristic of HT. Clonal bands were seen in three and a polyclonal smear pattern was seen in seven cases. The clonal bands in HT were associated with a background smear, and could not be reproduced from other blocks from the same case or from deeper sections of the same block. The clonal bands in thyroid lymphomas were not associated with a background smear and were reproducible. None of the patients with clonal B cells has developed malignant lymphoma during a follow up of 10-13 years.

CONCLUSIONS

B cell clonal bands in HT have different features from those in lymphoma (non-pure and non-reproducible) and do not predict future development of lymphoma.

Idiopathic Thrombocytopenic Purpura: Better Therapeutic Responses of Patients with B- or T-Cell Clonality than Patients without Clonality

Results of recent studies of the pathogenesis of idiopathic thrombocytopenic purpura (ITP) have suggested activated helper T-cells drive B-lymphocytes to produce antibodies. Twenty-eight children and 85 adults with ITP entered this study. We performed polymerase chain reaction (PCR) using framework III variable region (V(H) FRIII)- and joining region (J(H))-specific primers to analyze immunoglobulin heavy-chain gene rearrangement (IgH GR) for B-cell clonality. We used multiplex PCR to analyze T-cell receptor (TCR) gamma-chain gene rearrangement (TCRgamma GR) for T-cell clonality. We diagnosed 10 cases as acute ITP and 97 cases as chronic ITP. The IgH GR result was positive in 77.8% of the acute-form cases and in 58.8% of the chronic-form cases. The TCRgamma GR result was positive in 11.1% of the acute cases and in 10.6% of the chronic cases. There was no difference in frequency of clonality between the acute and chronic forms. After treatment the platelet count normalized in 81.8% (36/44) of the chronic ITP cases with B-cell clonality and in 88.9% (8/9) of the chronic ITP cases with T-cell clonality, compared with a normalized platelet count in 46.2% (12/26) of the chronic ITP cases without clonality. The patients with T- or B-cell clonality appeared to have better therapeutic responses than patients without clonality. In conclusion, T- and B-cell clonality may play a positive role in determining therapeutic response.

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.

Ocular adnexal lymphoid proliferations: clinical, histologic, flow cytometric, and molecular analysis of forty-three cases

PURPOSE

To describe the clinical features, histologic findings, flow cytometric immunophenotypes, and molecular profiles of ocular adnexal lymphoid proliferations.

STUDY DESIGN

Prospective noncomparative case series.

PARTICIPANTS

Forty-three patients suspected of having ocular adnexal lymphoid proliferations were biopsied and prospectively evaluated.

METHODS

Provisional diagnoses were made on the basis of routine histology and immunohistochemistry for B and T cells. Results of flow cytometric immunophenotyping (FCI) and molecular assessment using polymerase chain reaction for immunoglobulin heavy chain (IgH) and TCR gamma chain gene rearrangement and bcl-2/IgH translocation were then incorporated into a final diagnosis. Demographic and clinical outcome data were collected.

MAIN OUTCOME MEASURES

Final diagnosis based on histology, flow cytometry, and polymerase chain reaction.

RESULTS

Forty-three cases were studied. Final diagnoses included 17 lymphomas, 18 chronic inflammations, 4 reactive lymphoid hyperplasias, and 4 atypical lymphoid infiltrates. Preliminary evaluation accurately categorized all 43 cases as either lymphoma or nonlymphoma. FCI permitted more precise subclassification of the lymphomas according to the Revised European American Lymphoma (REAL) system of nomenclature as follows: eight marginal zone B cell (mucosa-associated lymphoid tissue type), three mantle cell, two follicular, three large cell, and one lymphoplasmacytoid lymphoma. FCI showed a clonal B cell proliferation in 94% (16 of 17) of the lymphomas; FCI identified a clonal B cell population in 4% (1 of 25) of cases of nonlymphomas. Molecular evidence of clonality was identified in 88% (15 of 17) of lymphomas, 39% (7 of 18) of chronic inflammations, and 50% (4 of 8) of reactive lymphoid hyperplasias and atypical lymphoid infiltrates.

CONCLUSIONS

The histologic diagnosis of ocular adnexal lymphoid lesions is highly accurate when determined by an experienced pathologist. FCI refines the histologic diagnosis and classification. Results of molecular studies should be interpreted in conjunction with clinical, histologic, and immunophenotyping findings.

IgH PCR of zinc formalin-fixed, paraffin-embedded non-lymphomatous gastric samples produces artifactual "clonal" bands not observed in paired tissues unexposed to zinc formalin

Helicobacter pylori (HP) causes dense gastritis that can be difficult to distinguish morphologically from MALT-type lymphoma (ML). Immunoglobulin heavy chain (IgH) gene analysis by polymerase chain reaction (PCR) is often used to resolve diagnosis. However, monoclonal bands have been reported in nonmalignant cases of gastritis. Retrospectively, 16 gastric ML with both formalin-fixed, paraffin-embedded (FF-PE) and ethanol-fixed samples (EF), and 9 cases of FF-PE HP-gastritis were analyzed by IgH PCR to document the presence of non-reproducible bands in HP-gastritis, but not ML samples. In duplicate analyses, 12 of 16 ML yielded identical monoclonal bands in FF-PE and EF samples whereas 3 of 9 FF-PE gastritis cases yielded different-sized (ie, non-reproducible) "clonal" bands. Sequencing of two PCR products from a gastritis case confirmed IgH gene sequences. To investigate whether FF-PE had a direct effect on producing these non-reproducible bands, 7 gastrectomy samples were prospectively divided into EF and FF-PE halves for IgH PCR. All 7 samples demonstrated polyclonal smears in EF portions while 4 of 7 FF-PE portions yielded either multiple distinct bands or non-reproducible bands. In conclusion, IgH PCR of FF-PE tissue can create artifactual "clonal" bands, which are the appropriate product size, contain IgH sequences, and, if not performed in duplicate, may confuse interpretation of B-cell clonality.

The natural history of a gastric low grade B cell MALT lymphoma followed during 11 years without treatment

Low grade B cell mucosa associated lymphoid tissue (MALT) lymphoma of the stomach is usually an indolent tumour that remains localised for a long time before dissemination occurs. MALT appears in the stomach in response to infection by Helicobacter pylori, which is present in 80-90% of cases. The pathogenesis of the evolution from chronic gastritis to malignant lymphoma has not yet been fully explained and the exact role of H pylori in the pathogenesis and progression of gastric lymphoma remains unclear. This report describes the case of a 72 year old woman with a low grade B cell MALT lymphoma localised in the gastric fundus, who refused to be treated for eradication of H pylori. The histological diagnosis of B cell MALT lymphoma was supported by both immunohistochemical and molecular genetic analysis. After 11 years of follow up, this MALT lymphoma remained indolent, without local progression or blastic transformation, and the H pylori infection was still persistent, even though the density of bacteria had decreased drastically. Interestingly, two different clonal immunoglobulin (Ig) gene rearrangements were found in two series of biopsies performed with an interval of 11 years. This case report supports the following notions: (1) H pylori associated gastritis is a risk factor for gastric MALT lymphoma, but might not be sufficient by itself for the progression of the disease, and (2) in the evolution of MALT lymphomas, different cell clones characterised by different Ig rearrangements may emerge.

Polymerase chain reaction-based diagnosis of bone marrow involvement in 170 cases of non-Hodgkin lymphoma

BACKGROUND

Up to the current time, diagnosis of bone marrow (BM) involvement in non-Hodgkin lymphoma (NHL) has been based on morphologic findings. Polymerase chain reaction (PCR) for antigen receptor gene rearrangements has the potential to increase the detection sensitivity of minimal degrees of BM involvement. The authors therefore assessed PCR-based clonalities of BM concurrently with morphology from 170 cases with NHL and evaluated the usefulness of comparative analysis of clonalities between bilateral BMs and the lymph node and the clinical significance of PCR based clonalities of BM.

METHODS

Bilateral BM clot sections of 170 cases and 47 lymph nodes were tested for immunoglobulin heavy chain gene rearrangement or T-cell receptor gamma gene rearrangement according to the B- or T-lineage of the lymph node.

RESULTS

When compared with morphology, the results of PCR showed an unexpectedly low positive concordance rate of 61.0% for B-cell NHL and 57.1% for T-cell NHL. When the clonality of BM was compared with that of lymph nodes in B-cell NHL, bilateral clonalities of BM showed high concordance with the clonality of the lymph nodes. PCR-based clonality did not show significant impact on survival.

CONCLUSIONS

Morphology remains the gold standard in the evaluation of BM involvement by NHL. Although the comparative analysis of BM clonality and that of the lymph nodes is considered a valuable tool that increases the reliability of clonality, PCR-based clonality of BM does not significantly add to the sensitivity of diagnosing BM involvement by NHL.

Primary low-grade MALT lymphoma of the gallbladder

We report a case of primary low-grade B-cell lymphoma of the mucosa-associated lymphoid tissue (low-grade MALT lymphoma) in the gallbladder. A 58-year-old woman suspected of gallbladder carcinoma underwent laparoscopic cholecystectomy. Microscopic examination of the gallbladder demonstrated lymphoid cell infiltration forming lymphoid follicles with hyperplastic secondary follicles. The surrounding monocytoid B cells and centrocyte-like cells selectively infiltrated the crypt epithelium forming lympho-epithelial lesions. Plasma cells were also noted beneath the mucosal epithelium. Bile culture revealed the Gram-negative bacilli Enterococcus faecalis and Morganella morganii. Immunoglobulin heavy chain gene rearrangement was confirmed using polymerase chain reaction (PCR) and oligoclonal lymphoid proliferations was detected. Because autoimmune diseases, or chronic inflammatory disorders, seem to correlate with the occurrence of MALT lymphoma, Gram-negative bacterial infection could also be considered as a prodrome of MALT lymphoma of the gallbladder.

Clonal evolution of gastric lymphoma of mucosa-associated lymphoid tissue type

Development of multiple lesions is frequent in gastric lymphoma of mucosa-associated lymphoid tissue (MALT) type. Presence of clonal components in multiple lesions was examined on the resected samples from 18 cases by using PCR-based method for immunoglobulin heavy-chain gene rearrangement. There were two or more lesions in 10 cases, and 2 to 12 samples were obtained from each lesion. The remaining eight cases had a single large lesion, from which two to six samples were collected from separate areas from each other. A total of 86 samples were analyzed. Histologic findings in each sample were categorized as follows: proliferation of exclusively centrocyte-like cells (CCL), large cells, and combined CCL and large cells. Monoclonal or biclonal pattern (single or two bands) was observed in 42 samples, oligoclonal pattern (three or more bands) in 30, polyclonal (smear) in 11, and no products in 3. Large-cell-type lesions showed fewer bands than those with other histologic types, and 75% of cases with large-cell type had mono- or biclonal proliferation. Common clones were found among lesions in about 60% of cases. Especially in 4 cases including 2 cases with large-cell type, every lesion in the same case contained the common clones. These findings suggested that gastric MALT lymphoma started as multi- or oligoclonal proliferation of cells, in which separate lesions composed of different clones from each other. As disease advances, dominant clones appear in some lesion and disseminate to other lesions via homing properties of the proliferating B lymphocytes.

Biclonality of gastric lymphomas

The pathogenesis and clonal evolution of gastric diffuse large B-cell lymphoma (DLBCL) and its relationship to extranodal marginal zone B-cell lymphoma (MZBL), mucosa-associated lymphoid tissue (MALT) type, are still controversial. The aim of this study was to establish the clonality of morphologically distinct areas of gastric lymphomas as well as their genetic relationship to each other. Six gastric lymphomas, consisting of two MZBL, MALT type, two DLBCL, and two "composite" lymphomas were subjected to laser capture microdissection and subsequent PCR-based amplification of the immunoglobulin heavy chain gene. One DLBCL showed a biclonal pattern of rearranged immunoglobulin heavy chain (IgH) genes of two different areas without evidence of a common origin. Two composite DLBCL with areas of extranodal MZBL, MALT type, were also biclonal and displayed different IgH gene rearrangements in the small-cell and in the large-cell components, respectively. Sequencing of the CDR3 region revealed unique VH-N-D and D-N-JH junctions, thus corroborating the presence of two genuinely distinct tumor clones in each of these three cases. In contrast, the remaining three gastric lymphomas (one DLBCL and two MZBL, MALT type) showed IgH gene rearrangements in which CDR3 regions were identical in the different tumor areas. Our results suggest that gastric DLBCL may be composed of more than one tumor cell clone. Further, DLBCL may not necessarily evolve by transformation of a low-grade lymphoma, but may also originate de novo. An ongoing emergence of new tumor clones may considerably hamper molecular diagnosis and follow-up of gastric DLBCL.

Are lymphocytic monoclonality and immunoglobulin heavy chain (IgH) rearrangement premalignant conditions in chronic gastritis?

Normal gastric mucosa is devoid of lymphoid cells. Any increase of lymphocytes suggests chronic inflammation. Infection with Helicobacter pylori (Hp) is the major cause for nonautoimmune chronic gastritis and induces a mixed cellular response resulting in an acquired lymphoid tissue, or MALT (mucosa-associated lymphoid tissue). Hp has also been implicated in the genesis of gastric MALT-lymphoma. Polymerase chain reaction-based assays to detect the expansion of monoclonal B-cells have also been used to corroborate the diagnosis. In a considerable number of cases monoclonal B-cells remain detectable in follow-up biopsies, with the lymphoma being in complete histological remission. The clinical relevance of this finding is not clear yet. However, there also exist different reports that monoclonal B-cells can be found in gastric biopsies of patients with neither a histological sign nor a present or past history of lymphoma. In the light of these findings we address the question whether B-cell monoclonality can be seen as a premalignant condition in chronic gastritis and conclude that as of now the relevance of the finding of B-cell monoclonality remains unclear. As of now the only and gold standard for the diagnosis of gastric MALT-lymphoma is histopathology.

Pulmonary Langerhans' cell histiocytosis: molecular analysis of clonality

Pulmonary Langerhans' cell histiocytosis (LCH) is a form of Langerhans' cell disease that primarily affects smokers in the third to fifth decade. Extrapulmonary manifestations are rare. Its clinical course is typically characterized by stabilization or regression of bilateral micronodular infiltrates seen on chest radiographs; progression to honeycomb fibrosis is rare. Because the clinical course of pulmonary LCH is distinct from systemic multiorgan LCH, currently thought to be a clonal proliferative disorder, we examined the X-linked polymorphic human androgen receptor assay (HUMARA) locus to assess clonality in female patients with one or more discrete LCH cell nodules in open lung biopsies. Langerhans' cells (LCH cells) were excised from formalin-fixed, paraffin-embedded tissue by microdissection to assure a relatively pure cellular population, and studies for differential methylation patterns at the HUMARA locus were performed. Twenty-four nodules in 13 patients were evaluated. Seven (29%) were clonal and 17 (71%) were nonclonal. Of six cases with multiple discrete nodules, three (50%) showed a nonclonal LCH cell population. In one biopsy with five nodules, two nodules were clonal with one allele inactivated, one nodule was clonal with the other allele inactivated, and two nodules were nonclonal. In contrast to systemic LCH, pulmonary LCH appears to be primarily a reactive process in which nonlethal, nonmalignant clonal evolution of LCH cells may arise in the setting of nonclonal LCH cell hyperplasia. Cigarette smoking may be the stimulus for pulmonary LCH in contrast to other forms of LCH.

Clonal proliferation of B lymphocytes in the germinal centers of human reactive lymph nodes: possibility of overdiagnosis of B cell clonal proliferation

Clonal expansion of the germinal center B cells of human reactive lymph nodes was analyzed. By micromanipulation, 28 germinal centers were microdissected from three nonneoplastic lymph nodes that had been fixed with formalin. Immunoglobulin heavy chain variable (V) region gene rearrangement was examined by seminested polymerase chain reaction (PCR) using two sets of primers (FR2-J and FR3A-J). An oligoclonal development (one to five clones) was found in each germinal center. Depending on the primer used, four or five (16%) of the germinal centers showed a single rearrangement band. The average number of B-cell clones in each germinal center was approximately 2.5. Next, the authors analyzed 50 endoscopic biopsy specimens from 6 patients with non-mucosa-associated lymphoid tissue (MALT) type gastric lymphoma, 25 patients with chronic gastritis, and 19 patients with nonspecific colitis. In addition to the samples from the 6 patients with malignant lymphoma, 8 of 44 biopsy samples (18.2%) from patients diagnosed as having chronic gastritis or nonspecific colitis showed one or two amplified bands. These results indicate that PCR analysis of immunoglobulin heavy chain V region gene rearrangement in small biopsy specimens could be misleading, causing overdiagnosis of reactive lymphoid tissue as B-cell clonal proliferation.

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

BACKGROUND/AIMS

Detection of clonal immunoglobulin heavy chain (IgH) rearrangements by the polymerase chain reaction (PCR) is an attractive alternative to Southern blotting in lymphoma diagnostics. However, the advantages and limitations of PCR in clonality analysis are still not fully appreciated. In this study, clonality was analysed by means of PCR, focusing in particular on the sample size requirements when studying extremely small samples of polyclonal and monoclonal lesions.

MATERIALS/METHODS

High resolution complementarity determining region 3 (CDR3) PCR was used to investigate the minimum number of cells and the amount of tissue required for the detection of a polyclonal population, both for fresh cells and formalin fixed, paraffin wax embedded tissue. Subsequently, frozen and paraffin wax embedded samples of 76 B cell lymphoproliferative disorders, 43 of which were tested by means of Southern blotting, were analysed to establish the sensitivity of this assay. These specimens included 12 chronic lymphocytic leukaemias (CLLs), nine mantle cell lymphomas (MCLs), 10 follicular lymphomas (FLs), and 45 mucosa associated lymphoid tissue (MALT) lymphomas. The specificity was tested on reactive lymph nodes (n = 19), tonsils (n = 4), peripheral blood lymphocyte fractions (n = 4), and biopsies with gastritis (n = 21).

RESULTS

In reactive tissue, 20 ng of high molecular weight DNA derived from 6.5-9 x 10(3) B cells was sufficient to obtain a polyclonal PCR result. With smaller amounts "pseudoclonality" could be induced. When using paraffin wax blocks, undiluted DNA isolated from tonsillar tissue of at least 1 mm2 was necessary to obtain a polyclonal pattern. The sensitivity required to detect clonality in paraffin wax embedded and frozen tissue by PCR for FL (40% and 60%, respectively) was lower than that for MALT lymphomas (60% and 86%, respectively), CLL (78% and 89%, respectively), and MCL (88% and 100%, respectively). PCR specificity was 96% and 100% for frozen and paraffin wax embedded tissue, respectively.

CONCLUSION

The minimum amount of template for CDR3 PCR is approximately 20 ng of high molecular weight DNA or 1 mm3 of B cell rich paraffin wax embedded normal tonsillar tissue, but care has to be taken to avoid pseudoclonality when low numbers of B cells are present. Duplicate or triplicate tests should be performed to avoid misinterpretation. The specificity of the PCR assay is almost 100%, whereas sensitivity depends on a combination of factors, such as lymphoma type and tissue fixation. Because frozen samples yield better results, obtaining fresh material for the PCR assay is recommended, especially when analysing FL and MALT lymphomas.

PCR analysis of the immunoglobulin heavy chain gene in polyclonal processes can yield pseudoclonal bands as an artifact of low B cell number

Polymerase chain reaction (PCR)-based analysis for detecting immunoglobulin heavy chain gene (IgH) rearrangements in lymphoproliferative disorders is well established. The presence of one or two discrete bands is interpreted as a monoclonal proliferation, whereas a smear pattern represents a polyclonal population. Prompted by our observation of discrete bands in histologically reactive processes with a relative paucity of B cells, we sought to determine whether low numbers of B cells in biopsy specimens could artifactually produce pseudomonoclonal bands. We performed IgH PCR analysis on serially diluted DNA samples from 5 B cell non-Hodgkin's lymphomas (B-NHLs), 5 reactive lymph nodes, 5 reactive tonsils and 10 microdissected germinal centers from a lymph node with follicular hyperplasia. We also assessed multiple aliquots of DNA samples from small biopsy specimens of reactive lymphocytic processes from the stomach (5 cases). PCR products were evaluated using high resolution agarose or polyacrylamide gels, and DNA sequencing was performed on IgH PCR products from two reactive germinal centers, which yielded monoclonal bands of identical size. All 5 B-NHLs harboring monoclonal B cell populations yielded single discrete bands, which were maintained in all dilutions. By contrast, all of the reactive lesions with polyclonal patterns at 50 ng/microl starting template concentration showed strong pseudomonoclonal bands at dilutions of 1:1,000 to 1:1,500 in placental DNA. Two of the microdissected reactive germinal centers that showed bands of identical size on duplicate reactions were proven to have different IgH sequences by sequencing. We conclude that specimens containing low numbers of polyclonal B cells may produce pseudomonoclonal bands on IgH PCR analysis. IgH PCR analysis should be performed on multiple aliquots of each DNA sample, and only samples that yield reproducible bands of identical size can be reliably interpreted as monoclonal.

Distinct B-cell clonal bands in Helicobacter pylori gastritis with lymphoid hyperplasia

Helicobacter pylori (Hp)-associated gastritis is a risk factor for gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Clonal B-cell populations are present in both reactive and neoplastic MALT tissue, thus limiting their usefulness in the evaluation of gastric lymphoid infiltrates in endoscopic biopsy specimens. The aim of this study was to identify the presence of clonal B-cell populations in Hp-gastritis with MALT and to assess their usefulness in distinguishing reactive from malignant infiltrates. Routinely fixed paraffin-embedded blocks from 20 patients with Hp-gastritis with lymphoid hyperplasia were analysed for B-cell clonality by a semi-nested polymerase chain reaction (PCR) using FRIII/LJH and FRIII/VLJH primers for amplification of the VDJ region of the immunoglobulin heavy chain gene. The histopathological findings were evaluated according to a previously published scoring system. Immunohistochemistry was performed by the labelled streptavidin-biotin technique using the following primary antibodies: CD45, CD45RO, CD3, CD20, and cytokeratin. The histopathological findings were diagnostic of Hp-chronic active gastritis (grade 2, n=17; grade 3, n=3). Scattered intraepithelial B-cells were present in all cases and non-destructive lymphoepithelial lesions in one grade 3 case. Amplifiable DNA was obtained from all samples. Clonal bands were observed in ten (7/17 grade 2 and 3/3 grade 3 lesions) and polyclonal smears in ten cases (all grade 2). The clonal bands were often (n=6) associated with a background polyclonal smear and were not reproducible from deeper sections (n=10) or another paraffin block (n=1), while the clonal bands in control low-grade MALT lymphomas were not associated with a background smear and were reproducible from deeper sections. None of the patients has developed lymphoma to date (follow-up 21-44 months). In conclusion, B-cell clonal bands are common in H. pylori-gastritis with lymphoid hyperplasia. The irreproducibility of these bands is a useful feature in favouring a reactive process.

Evaluation of lymphoid cell populations in cytology specimens using flow cytometry and polymerase chain reaction

Differential diagnosis between lymphomas and reactive lymphoid proliferations often requires ancillary techniques and morphologic evaluation. Flow cytometry (FCM) and polymerase chain reaction (PCR) can aid the detection of monoclonal B-cell populations. In the present study, the sensitivity and specificity of these two methods in the study of cytology specimens were compared. Eighty-six cytologic specimens from 81 patients (lymph nodes, solid organs, and body cavities) were evaluated. These specimens were taken from three groups of patients: those who underwent an initial evaluation for suspected lymphoma; those who were previously diagnosed with B-cell lymphoma and were now evaluated for possible disease recurrence; and those who were diagnosed with a nonhematologic malignancy. Histologic diagnosis was available for 51 samples. All samples were tested by FCM for the detection of monoclonality using kappa:lambda ratio and for clonal immunoglobulin heavy chain (IgH) gene rearrangements using a single-round PCR after cytologic evaluation. Tissue morphology, FCM and PCR results, and clinical findings in specimens without histologic diagnosis were correlated. Histologic evaluation (N = 51) revealed 44 specimens with B-cell malignancy. Twenty of the 44 lymphoma specimens (45%) were accurately diagnosed in cytologic smears, 18 (41%) were classified as suspicious of lymphoma, and 6 (14%) were diagnosed as reactive. FCM had superior sensitivity compared with PCR (77% vs. 64%). Fifty-six percent of specimens with B-cell malignancy were FCM+/PCR+, 23% were FCM+/PCR-, 14% were FCM-/PCR+, and 7% were FCM-/PCR-. The combined use of FCM and PCR resulted in a diagnosis of B-cell lymphoma in 41 (93%) of 44 B-cell lymphoma specimens and increased the sensitivity of fine needle aspiration by 48%. Both FCM and PCR aid in the diagnosis of lymphoid lesions in cytology specimens, and both can detect monoclonal B-cell populations that may be interpreted in cytology smears as reactive, even by experienced cytologists. Although FCM had higher sensitivity than PCR test in the present study, their combined use should be considered because of a relatively large number of specimens that were detected as monoclonal only with PCR.

Molecular genetics of extranodal marginal zone (MALT-type) B-cell lymphoma

Mucosa-associated lymphoid tissue lymphoma is now classified as extranodal marginal zone B-cell lymphoma. We reviewed the current literature on the biological and genetic mechanisms that lead to the development and progression of this unusual lymphoma. Particular attention was given to the clinical and biological significance of the immunoglobulin genes rearrangement, that has been proposed and widely used both diagnostically and as a tool to monitor the response to antibiotic treatment.

Onset and dynamics of osteosclerosis in mice induced by Reilly-Finkel-Biskis (RFB) murine leukemia virus. Increase in bone mass precedes lymphomagenesis

Newborn NMRI strain mice were infected with Reilly-Finkel-Biskis (RFB) murine leukemia virus (MuLV), a murine leukemia virus that has been shown to induce lymphomas, osteosclerosis, and osteomas in susceptible strains of mice. Bone histomorphometry of the distal femoral metaphyses at 3-month intervals showed osteosclerosis 3 (100%), 6 (100%), and 9 (93%) months after infection. This was represented by significantly augmented cancellous bone mass and accompanied by distinct changes in bone architecture. High numbers of provirus copies were detected at 2-4 weeks in femora, humeri, and calvaria, and viral protein was highly expressed in trabecular and cortical bone cells, particularly in osteocytes. Infected mice showed enhanced bone formation and smaller numbers of osteoclasts relative to sex- and age-matched controls. Osteoclastic differentiation was significantly reduced in cocultures of spleen or bone marrow cells with RFB MuLV-infected osteoclastogenic, osteoblast-like cells. However, RFB MuLV did not impair the activity of mature osteoclasts. In infected mice lymphomas were only observed at 6 (22%) and 9 months (40%) of age. At 3 months, IgG gene and TCR-beta gene rearrangements were not detectable, and new proviruses showed a heterogeneous integration pattern, indicating the absence of lymphoma in early osteosclerotic mice. In contrast, lymphomas, which developed in 8- to 9-month-old infected mice, showed IgG rearrangements indicating development of B-cell lymphomas, together with mono- or oligoclonal expansion of distinct patterns of proviral integrations. These results indicate that RFB MuLV-induced osteosclerosis develops within 3 months after infection and precedes lymphomagenesis. It may therefore be considered an independent skeletal lesion in MuLV-infected mice.

Detection of immunoglobulin heavy chain gene rearrangements by polymerase chain reaction analysis on lymph node imprints and fine-needle aspirate smears: a comparison of five different imprint preparations

Five different preparations of lymph node imprints from 39 patients were studied to determine which preparations are suitable for obtaining interpretable results with polymerase chain reaction (PCR)-based detection of immunoglobulin heavy chain gene rearrangements and whether there are significant discrepancies in the patterns obtained. The sensitivity and specificity of this test for the diagnosis of B-cell lymphoma were assessed. The five imprints were stained with May-Grünwald-Giemsa (MGG) and coverslipped, stained with MGG but not coverslipped, fixed in acetone only, air-dried only, or immunostained, respectively. The efficiency of the PCR was 0% for immunocytochemically stained slides, 87% for air-dried only and air-dried/MGG-stained/coverslipped slides, 95% for air-dried/MGG-stained/not coverslipped slides, and 100% for imprints that were air-dried/acetone-fixed. There was total agreement in results in 87% cases studied. Discrepancies never resulted in false-positive test results. The overall sensitivity was 50%, and specificity was 100%. Based on these results, we have devised guidelines for tissue treatment when only stained slides are available. In a prospective study with 19 fine-needle aspirate specimens, the efficiency of the PCR increased to 100%, and sensitivity improved to 81%.

PCR-based clonality analysis: a reliable method for the diagnosis and follow-up monitoring of conservatively treated gastric B-cell MALT lymphomas?

AIMS

We evaluated polymerase chain reaction (PCR) amplification of specific immunoglobulin heavy chain (IgH) gene rearrangements as a means of demonstrating monoclonality during follow-up of conservatively treated gastric MALT lymphoma, and compared the reproducibility of PCR on sequential frozen and paraffin-embedded endoscopic biopsies. We established an association between clonality detected by PCR and the histological observations.

METHODS AND RESULTS

Sixty-nine pairs of sequential frozen and paraffin-embedded endoscopic biopsies from 21 conservatively treated patients were graded according to the Wotherspoon-Isaacson histological scoring system, which provides a measure of diagnostic confidence on a scale 0-5. PCR amplification of the IgH gene was performed using FR3/JH and FR2/JH primers. 68/69 paired samples (98.5%) showed identical mono- or polyclonal PCR amplification patterns. Forty-seven out of 48 pairs of samples sharing similar histological features produced identical amplification patterns in both fresh and paraffin-embedded tissues. In comparison with the histological grading, monoclonality was detected in 64.2% and 41.6% of samples scored 5 and 4, respectively. Conversely, among 64 samples scored 0-3, a monoclonal pattern was observed only in two samples, one of which was from a patient who relapsed 9 months later.

CONCLUSIONS

PCR-based clonality analysis by demonstration of specific IgH gene rearrangement can be easily and reliably performed on both frozen and paraffin-embedded endoscopic biopsies. In conjunction with histological observation, this method can be used as a complementary tool to monitor MALT lymphoma regression during conservative treatment.

Detection of clonal B cells in microdissected reactive lymphoproliferations: possible diagnostic pitfalls in PCR analysis of immunoglobulin heavy chain gene rearrangement

AIMS

To evaluate the specificity of standard and fluorescence based (Genescan) polymerase chain reaction (PCR) immunoglobulin heavy chain (IgH) gene rearrangement analysis in complete and microdissected paraffin wax embedded sections from lymphoid proliferations.

METHODS

PCR IgH gene rearrangement analysis of whole sections and microdissected fragments (n = 62) from paraffin wax embedded reactive lymph nodes (n = 6) and tonsils (n = 3). Amplificant analysis used both standard methods and automated high resolution fluorescence based quantification and size determination using GENESCAN software.

RESULTS

Whole tissue sections were consistently polyclonal in control experiments. IgH gene amplification was successful in 59 of 62 microdissected fragments; only two of 59 showed a polyclonal rearrangement pattern, the remainder being oligoclonal or monoclonal. Reanalysis was possible in 33 samples; six showed reproducible bands on gel analysis and satisfied accepted criteria for monoclonality. Use of high resolution gels with Genescan analysis improved sensitivity and band definition; however, three samples still appeared to be monoclonal.

CONCLUSIONS

These results confirm that PCR based IgH gene rearrangement analysis is a sensitive and specific method for demonstrating B cell clonality in whole paraffin wax embedded sections. However, oligoclonal and monoclonal rearrangement patterns are regularly encountered in small tissue fragments from otherwise unremarkable reactive lymphoproliferations, possibly because of preferential priming or detection of local B cell clones. Data from clonal analysis of small, microdissected or lymphocyte poor samples must be evaluated critically. It is recommended that analyses should be run in parallel on at least two tissue specimens. Only reproducible bands present in more than one sample should be considered to be suggestive of neoplasia.

Distinct clonal origin of low-grade MALT-type and high-grade lesions of a multifocal gastric lymphoma

AIMS

Low-grade mucosa-associated lymphoid tissue (MALT) lymphoma and high-grade B-cell non-Hodgkin's lymphoma (NHL) of the stomach may occur simultaneously. To determine the clonal relationship between these tumours, we compared the immunoglobulin heavy chain gene (IgH) rearrangements of low and high-grade components of a multifocal gastric NHL.

METHODS AND RESULTS

The complementary determining region 3 (CDR3) of the IgH gene rearrangements were polymerase chain reaction (PCR) amplified, cloned and sequenced. The analysis of the CDR3 sequences rearranged by tumour cells of low-grade MALT and the high-grade NHL revealed different nucleic acid sequences.

CONCLUSION

These findings suggest that low-grade MALT and high-grade B-cell components of multifocal gastric NHL may represent unrelated clones.

Clinical and pathologic characterization of mucosa-associated lymphoid tissue lymphoma of the head and neck

Mucosa-associated lymphoid tissue (MALT) has recently been recognized as a possible site of origin for low-grade lymphomas of the B-cell type. Though relatively rare, these MALT lymphomas may arise within several sites in the head and neck, and often present diagnostic and therapeutic challenges. We review 4 cases of primary MALT lymphoma of the head and neck, treated with surgical excision (3 cases), irradiation (2 cases), and chemotherapy (1 case), to further characterize this new subtype of head and neck malignancy. The mean time from onset of symptoms to histologic diagnosis was 15 months. Fine needle aspiration identified an atypical lymphoid infiltrate in only 1 of 3 patients. Immunohistochemical analysis was essential in establishing the diagnosis of MALT lymphoma in all 4 of the cases, and demonstrated characteristic negative staining for CD3, CD5, and CD43, positive staining for CD20, and monotypic staining for either kappa or lambda light chain immunoglobulin markers. All patients achieved complete remission after primary therapy, and all remain free of disease with follow-up ranging from 6 to 54 months (mean 33 months). The diagnosis of MALT lymphoma should be considered in cases of atypical lymphoid infiltrates in the head and neck, and increased awareness coupled with detailed immunohistochemical analysis is essential to securing an accurate diagnosis. Clinical remission of MALT lymphoma may be achieved with several modalities, but further study will be required to determine the long-term response to treatment.

Low prevalence of monoclonal B cells in Helicobacter pylori gastritis patients with duodenal ulcer

We have studied the prevalence of B-cell clonality among a large group of 320 patients with Helicobacter pylori gastritis and duodenal ulcer. These patients underwent endoscopic examination with multiple gastric biopsies at diagnosis and were followed 2 and 12 months after therapy. Histopathologic examination of 809 sets of biopsy specimens showed lymphoid gastritis with lymphoid aggregates or follicles, but without lymphoepithelial lesion, in 302 samples corresponding to initial biopsy specimens (n=130) or to posttreatment biopsy specimens (n=172). DNA extracted from fresh antral specimens allowed the amplification of Helicobacter pylori DNA in all cases before therapy. The arrangement of the immunoglobulin heavy chain gene was studied by polymerase chain reaction (PCR) in the 302 selected lymphoid gastritis samples. Single or dominant bands were seen only in four specimens from three patients (1.3%), whereas a polyclonal pattern was seen in the other 298 samples. The detection threshold of our PCR technique was approximately 3% of clonal B cells diluted in a polyclonal population. This threshold appeared to be a reliable cutoff between polyclonal gastritis and clonal MALT lymphoma. In our experience, Helicobacter pylori lymphoid gastritis appeared mainly as a benign polyclonal condition.