This is an observational study with a case control design. This study included patients with gastric cancer confirmed by pathological diagnosis of gastric tissue, and matched the control population according to age, gender, etc. In this study, researchers collected clinical information and multiple biological samples such as serum and tissue tissue from the study subjects. The researchers combined exosome sequencing, proteomics and single-cell RNA sequencing to explore the heterogeneity of cardia cancer, identify specific biomarkers and potential therapeutic targets for cardia cancer, and provide a basis for the development of new diagnostic tools and therapeutic strategies.