Clonal Ig-gene rearrangement in some cases of gastric RLH detected by PCR method

Comparison of the DNA extraction methods for polymerase chain reaction amplification from formalin-fixed and paraffin-embedded tissues

To obtain an adequate quality and quantity of DNA from formalin-fixed and paraffin-embedded tissue, six different DNA extraction methods were compared. Four methods used deparaffinization by xylene followed by proteinase K digestion and phenol-chloroform extraction. The temperature of the different steps was changed to obtain higher yields and improved quality of extracted DNA. The remaining two methods used microwave heating for deparaffinization. The best DNA extraction method consisted of deparaffinization by microwave irradiation, protein digestion with proteinase K at 48 degrees C overnight, and no further purification steps. By this method, the highest DNA yield was obtained and the amplification of a 989-base pair beta-globin gene fragment was achieved. Furthermore, DNA extracted by means of this procedure from five gastric carcinomas was successfully used for single strand conformation polymorphism and direct sequencing assays of the beta-catenin gene. Because the microwave-based DNA extraction method presented here is simple, has a lower contamination risk, and results in a higher yield of DNA compared with the ordinary organic chemical reagent-based extraction method, it is considered applicable to various clinical and basic fields.

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.

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.

PCR analysis of IgH and BCL2 gene rearrangement in the diagnosis of follicular lymphoma in lymph node fine-needle aspiration. A critical appraisal

In order to improve the cytomorphologic diagnosis of malignant lymphoma on lymph node fine-needle aspiration (FNA), and to make a confident discrimination between low-grade follicular non-Hodgkin's lymphoma (NHL) and lymphoid hyperplasia, polymerase chain reaction (PCR) analysis was performed of the Ig CDR3 region and BCL2 breakpoint region in 25 nonselected cases of malignant lymphoma (17 NHL and 8 Hodgkin's disease [HD]) with histologic control, and 22 cases of lymph nodal hyperplasia with histologic and/or clinical control. Among lymphomas, IgH monoclonality was detected in 7 (77%) of 9 NHLs and BCL2 rearrangement in 3 (17.6%) of 17 NHLs, all of which were follicular centroblastic-centrocytic (FCBCC). Three BCL2/JH negative FCBCC cases were monoclonal for CDR3. Neither IgH monoclonality nor BCL2 rearrangement were found in HD. Among cytologically diagnosed lymphoid hyperplasias, one IgH polyclonal case was considered false-negative, being histologically diagnosed as lymphoplasmacytic NHL on the subsequent excisional biopsy. Another 4 cases (2 BCL2 rearranged and 2 monoclonal for IgH) were considered false-positive on the basis of histologic features or clinical control. These data indicate that the combined PCR analysis of IgH and BCL2 rearrangements can confirm a cytologic diagnosis of lymphoma in FNAs while, due to the occurrence of both false-positive and false-negative results, it is of limited value in the distinction between follicular lymphoma and lymphoid hyperplasia without morphologic or clinical support.

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

The polymerase chain reaction (PCR) with polyacrylamide gel electrophoresis was used to study patterns of immunoglobulin heavy chain (IgH) gene rearrangement (GR) in formalin-fixed, paraffin-embedded specimens of lymphomas and reactive conditions of mucosa-associated lymphoid tissue (MALT) and lymph node. DNA amplification was performed directly on sections obtained from paraffin blocks. Five patterns of PCR products were observed: a single band, two or more discrete bands, smearing, a single band overlying a smear, and two or more bands over a smear. A pure polyclonal pattern (smear) was observed in all of the reactive lymph nodes but in only 15% of cases of Helicobacter pylori (HP) gastritis with lymphoid hyperplasia, 25% of cases of HP gastritis without lymphoid hyperplasia, and 37% of colonic specimens of various types. Patterns consisting of multiple bands with or without background smearing were common in gastritis, colitis, and gastric lymphomas. Single bands or dominant bands were present in all lymph node and salivary gland lymphomas, 12 of 14 cases of gastric lymphoma, and 17 of 20 cases of HP gastritis with lymphoid hyperplasia. These bands were reproducible in deeper sections from the same paraffin block or similar areas sampled in different blocks in all of the lymph node and salivary gland lymphomas, 11 of 12 gastric lymphomas, but only 1 of 17 cases of HP gastritis with lymphoid hyperplasia. Bands were also found in 3 of 20 cases of HP gastritis without lymphoid hyperplasia and 17 of 38 colonic specimens, but these were not reproducible. The complexity of patterns of IgH GR in acquired MALT compared with lymph nodes may be the result of a relative paucity of B-cell clones or preferential proliferation of B-cell clones with a limited area of distribution.

Atypical lymphoid infiltrations of the gastric mucosa--their interpretation and management by eradication of Helicobacter pylori

Low-grade gastric lymphomas of mucosa-associated lymphoid tissue (MALT) may be extremely difficult to differentiate from atypical lymphoid infiltrations of the gastric mucosa caused by Helicobacter pylori (H. pylori) infection, especially if lympho-epithelial destructions are not detected. In order to clarify this diagnostic problem and to evaluate the potential benefit of clearing H. pylori-induced lymphoid infiltration a prospective study was performed. Our study included biopsy specimens from 61 patients, that showed excessive lymphoid infiltrations. Using histology and immunohistochemistry no definite diagnosis could be delivered. In 46 (76.4%) cases histological regression occurred 4 weeks after the end of therapy suggesting a reactive infiltrate. In 7 patients (11.5%) the histological picture remained unchanged, and in 8 (13.1%) the follow-up biopsies revealed lympho-epithelial destructions allowing the diagnosis of low-grade MALT lymphoma. On the basis of our data we conclude that eradication of H. pylori could provide an additional tool in the differential diagnosis between atypical lymphoid infiltrations of the gastric mucosa caused by H. pylori and an early primary gastric MALT lymphoma.

Epstein-Barr-virus-associated medullary carcinomas with lymphoid infiltration of the stomach

The association of Epstein-Barr virus (EBV) with gastric medullary carcinoma with lymphoid infiltration (GMCL) was investigated. The presence of GMCL exhibited a 2/1 male-to-female ratio and a 1/2 early-to-advanced cancer ratio, predominantly located in the cardia and corpus of the stomach (90%). The presence of EBV DNA could be proven in 28 out of 30 GMCL cases (93%) by the polymerase chain reaction method, and in 27 cases (90%) latent infection of EBV strictly limited to cancer cells was identified by in situ hybridization with RNA using an EBV-associated small RNAs (EBERs) probe. No histopathological difference was noted between EBERs-positive and -negative groups. Monoclonal EBV infection, identified by the length of lymphocyte-determined membrane antigen variable tandem repeats, was suggested in 19 out of 27 EBERs-positive cases (70.3%). However, only one case showed a positive reaction for anti-(latent membrane protein)-1 antibody, and none of the EBERs-positive cases bound anti-EBNA-2 antibodies, the respective antigens being considered oncoproteins directly linked with EBV-related B cell lymphomagenesis. In conclusion, while EBV is clearly present at extremely high incidence in GMCL, having characteristics biological features, a role for EBV in tumorigenesis of such lesions remains uncertain.

Molecular-genetic analysis of ocular adnexal benign lymphoid hyperplasias by a two-step polymerase-chain-reaction

Twelve biopsied ocular adnexal benign lymphoid hyperplasias (OABLH) satisfying benign histological criteria were investigated for clonal immunoglobulin (Ig) heavy-chain gene rearrangement by means of a two-step polymerase chain reaction (PCR) method using formalin-fixed and paraffin-embedded tissue. Of the 12, 4 (33%) demonstrated clear single bands of the rearranged gene for the Ig heavy-chain, of between 100 and 150 base pairs. The selected cases were all free of malignant lymphoma and all of the lesions were small (2 x 2-22 x 6 mm; median 4.5 x 3 mm). Histopathological and cytological features were not essentially different between monoclonal and non-monoclonal examples. Immunohistochemistry was of little benefit in separating the two. It is concluded that OABLH demonstrating a benign clinical course frequently contain monoclonal B cell populations suggesting a continuous progressive spectrum of lesions in B cell neoplasia. In addition, the significance of molecular-genetic analysis for OABLH and the utility of the two-step PCR method should be emphasized.