B-CELL MONOCLONALITY PRECEDES THE DEVELOPMENT OF GASTRIC MALT LYMPHOMA IN HELICOBACTER-PYLORI-ASSOCIATED CHRONIC GASTRITIS

Little is known about the temporal changes in Helicobacter pylori dens ity and B-cell clonality during the evolution from chronic gastritis t o gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Biopsied specimens from 28 patients with chronic gastritis who developed gastri c MALT lymphoma (group A) and from 24 similar patients who did not (gr oup B) during an equivalent follow-up period (mean, 42 months) were re trospectively scored for histological features of MALT lymphoma (0 to 5) and H. pylori density (0 to 3). B-cell clonality was analyzed by po lymerase chain reaction (PCR). During the observation period, the H. p ylori density in group A decreased significantly in comparison with gr oup B; the mean change in H. pylori density (final minus initial densi ty) per 1000 days was -1.4 for group A and +0.2 for group B (P < 0.005 ). Monoclonality was detected more frequently in group A (79%) than in group B (21%; P < 0.005), and it preceded the histological evidence o f malignant transformation in 64% of those patients who showed monoclo nality in group A. These results suggest that H. pylori is thus more c losely associated with the precursor or initial phase in the genesis o f gastric MALT lymphoma than with the later phase, as its density decr eases as the tumor progresses. The detection of B-cell monoclonality b y PCR is thus of possible use for predicting the histological genesis of gastric lymphoma.