Gastric Cancer Prevention: Understanding Precursor Lesions and Risk Factors for Progression to Cancer

Inclusion Criteria: * Age ≥ 18 years old * Able to read and understand English and Spanish * Meet criteria for one of three potentially eligible study populations: * Individuals with gastric atrophy, gastric intestinal metaplasia, or dysplasia: Had a previous diagnosis of or have been diagnosed by the investigation team with gastric atrophy, gastric intestinal metaplasia, or dysplasia of the gastric mucosa on pathology review from an endoscopic biopsy. Individuals who have a prior history of early gastric cancer may be included, if they were treated endoscopically and have no evidence of disease. Individuals who have a prior history of a cancer other than upper gastrointestinal cancer may also be included, if they have no evidence of disease for at least 1 year prior to study enrollment and are not undergoing active treatment for any malignancy at any time throughout the study period * Healthy controls (average risk): Individuals with no history of cancer or gastric precursor lesions undergoing a clinically indicated endoscopy at MSK for workup or dyspepsia or reflux * Gastric cancer cases: Individuals with a known diagnosis of early gastric adenocarcinoma undergoing surgical resection at MSK Exclusion Criteria: * Age \< 18 years old * Women who are pregnant (may be enrolled after delivery) * Individuals with a prior history of upper gastrointestinal surgery or a prior cancer who are undergoing active treatment for malignancy or have been diagnosed within 1 year prior to the study enrollment or with pancreatic cancer. (This does not include incidentally diagnosed primary gastric adenocarcinoma identified during study follow up. Individuals diagnosed with gastric carcinoid limited to the stomach will also be included, given their ongoing parallel risk for gastric adenocarcinoma.) * Have severe comorbidities with expected survival time \<2 years or which would prevent them from undergoing routine elective EGD (at the discretion of the patient's provider and the study team) * Individuals having Hereditary Diffuse Gastric Cancer Syndrome, mutations including CDH1 and CTNNA1, or more than one genetic mutation * Exclude high risk esophageal and duodenal lesions including: * Duodenal Adenoma * Dysplasia or cancer at the esophagus or gastroesophageal junction * Patients with an increased risk for biopsies during EGD, such as those with clotting disorders.