Background: Gastric cancer (GC) is major global health concern and the second leading cause of cancer deaths worldwide. Amplification of Her2/neu gene and/or overexpression of the Her2/neu protein have been observed in GC. Trastuzumab (Herceptin™) is an anti-Her2/neu antibody, which has been successfully applied in GC. However, the intratumoral heterogeneity of Her2/neu overexpression and amplification in GC should be noticed. The investigators investigated the significance of evaluating Her2/neu expression in different paraffin blocks of tumor tissue in GC.

Methods: 2000 GC patients from ten centers, patients were divided into a cohort using one tumor tissue paraffin block (cohort 1, n=1000) and a cohort using dual tumor tissue paraffin blocks (cohort 2, n=1000) when evaluating Her2/neu expression status by immunohistochemistry (IHC). In cohort 2, the investigators combined the results from two different paraffin blocks and used the higher one as the final score.

Inclusion Criteria:

• Undergone curative surgery of gastric cancer,
• 18-80 years old.

Exclusion Criteria:

• None

Undergone curative surgery of gastric cancer, 18-80 years old