Clinicopathologic analysis of gastric mucosa-associated lymphoid tissue lymphoma with or without c-Met expression.

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach is mainly associated with Helicobacter pylori infection, and H. pylori eradication therapy is often effective. However, 20-30% of the cases of MALT lymphoma are resistant to the eradication therapy, and translocation of the API2-MALT1 gene is often found in these cases. Most cases without translocation of API2-MALT1 are localized to the stomach, whereas some cases with this translocation are a more advanced stage of MALT lymphoma that spreads to other organs. The c-Met receptor is a prognostic factor involved in infiltration and metastasis in many malignant tumors, including gastric, pancreatic, lung, and kidney cancer. In the present study, the expression of c-Met in 43 cases of gastric MALT lymphomas was immunohistochemically examined and compared with clinicopathological factors. To elucidate the significance of c-Met in MALT lymphoma, the expression intensity of c-Met in 22 API2-MALT1 translocation-positive and 21 API2-MALT1 translocation-negative cases was scored, compared, and examined. The immunohistochemistry analysis revealed strong staining for c-Met in 21 API2-MALT1 translocation-positive cases and in 1 translocation-negative case (P = 0.00). This result indicates the relationship between strong expression of c-Met and the progression of MALT lymphoma with API2-MALT1 gene translocation.