Since SHP-2 closely interacts with the CagA protein, it is natural to speculate that functional polymorphisms in the PTPN11 (protein-tyrosine phosphatase, nonreceptor-type 11) gene encoding SHP-2 may ultimately influence the degree of gastric atrophy and transformation to gastric cancer in infected subjects. This evidence concerns the gene PTPN11 and chronic atrophic gastritis.