Prevalence of Helicobacter pylori infection in gastric MALT lymphoma: a systematic review

To perform a systematic review of studies evaluating H. pylori prevalence in patients with MALT lymphoma, and to analyze predictive factors of response. A literature search in Pubmed was performed of papers studying H. pylori prevalence in patients with MALT lymphoma. 38 studies were identified including 1,844 patients. The average prevalence of H. pylori infection was 79%. In patients diagnosed with H. pylori infection using 2 or more methods prevalence was 85%, whereas it was 77% when only one diagnostic method was used (p < 0.0001). H. pylori prevalence in patients diagnosed by histology was 75%, whereas it was 85% when serology was used (p < 0.0001). 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 reaching deeper beyond the submucosa (p < 0.0001). H. pylori prevalence in patients with MALT lymphoma is variable, and seems to depend, at least partly, on the number and type of diagnostic methods used, histologic grade, and deep tumor invasion. If appropriate diagnostic methods are used, 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.