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.