**2. The close link between** *Hp* **infection and gastric MALT lymphoma**

*Hp*, a gram-negative and spiral rod-shaped bacterium that has evolved to grow in the environment of the stomach, infects approximately 50% of the population worldwide [42, 43]. Epidemiologic studies have shown that the prevalence of *Hp* infection documented by the histological detection of bacteria or positive serology was significantly higher in gastric MALT lymphoma patients than in healthy populations [44, 45]. Asenjo et al. reviewed studies exploring the association between *Hp* prevalence and gastric MALT lymphoma patients, and revealed that the incidence of *Hp* was approximately 79% in 1844 patients with gastric MALT lymphoma, and the differential prevalence may result from the number of assessments of *Hp*

infection. For example, a higher positive rate of *Hp* infection is observed with the use of more than two methods than with the use of a single method [46]. Moreover, the *Hp* infection rate was 74% for patients whose tumors were limited to the mucosa or submucosa, whereas the *Hp* infection rate was 44% for patients whose tumors invaded the muscularis or beyond [46].
