PATHOGENESIS OF GASTRIC LYMPHOMA - THE ENIGMA IN HONG-KONG

Background: Helicobacter pylori (H. pylori) infection has been postula ted to be a pathogenetic factor in gastric lymphoma. However, the etio logical factors for gastric lymphoma could vary in different populatio ns. Materials and methods: We looked for histological evidence of H. p ylori infection in 53 gastrectomy specimens from Hong Kong Chinese pat ients with primary gastric B-lymphoma. We also screened for Epstein-Ba rr virus (EBV) in these cases using in situ hybridization with oligonu cleotide probes for EBV-encoded small RNA1 and 2. Results. H. pylori w as found in 29 of 53 (55%), including 8 of 13 (62%) cases of low-grade lymphoma of mucosa-associated lymphoid tissue (MALT) type. These infe ction rates in gastric lymphoma are lower than those reported in Weste rn populations (80%-100%) and comparable to that found in healthy Chin ese blood donors (55%) or in non-ulcer dyspeptic patients (52%-57%). E BV was found in tumor cells only in one case of high-grade gastric lym phoma with low-grade MALT component which was H. pylori-negative, and in occasional nontumor lymphoid cells in 7 other cases. Conclusions: T hese results suggest that (1) the role of H. pylori in pathogenesis of gastric lymphoma may vary in different populations; (2) Very few gast ric lymphomas are associated with EBV; (3) not all low-grade gastric M ALT lymphomas are H. pylori-dependent.