Prevalence of Helicobacter pylori infection in gastric MALT lymphoma

Objective: To perform a systematic review of the studies that evaluate Helicobacter pylori prevalence in patients with MALT lymphoma, and to analyze the predictive factors of response. Methods: A bibliographic search in Pubmed has been done selecting the articles that studied H. pylori prevalence in patients with MALT lymphoma. Results: 38 studies involving 1 844 patients were identified. The average prevalence of H. pylori infection was 79%. In patients diagnosed with H. pylori infection by 2 or more methods the prevalence was 85%, whereas it was 77% when only one diagnosis method was performed (p < 0.0001). The H. pylori prevalence in patients diagnosed with histology was 75%, but 85% when serology was used (p < 0.0001). The H. pylori prevalence in high grade lymphomas was 60% and 79% in low grade lymphomas (p < 0.0001). H. pylori infection was detected in 74% of lymphomas confined to the submucosa, but only in 44% of those deeper than the submucosa (p < 0.0001). Conclusions: H. pylori prevalence in patients with MALT lymphoma seems to vary according to the number and the type of diagnosis methods used to detect the infection, the histological grade and the depth of the tumoral invasion. If the appropriate diagnosis methods are performed and if only low grade lymphomas are considered, H. pylori prevalence is high, nearly 90%, which reinforces the role of these bacteria in gastric MALT lymphoma.