Brief Summary: RATIONALE: Studying samples of tissue, blood, urine, stool, and other biological fluids from patients with cancer and from healthy volunteers undergoing colonoscopy or endoscopy may help doctors identify and learn more about biomarkers related to cancer. PURPOSE: This research study is looking at gastrointestinal biomarkers in tissue and biological fluid samples from patients and participants undergoing colonoscopy, endoscopy, or surgery.

Detailed Description: OBJECTIVES: * Identify new potential biomarkers of increased gastrointestinal cancer risk using tissue and biofluid samples from patients and volunteers undergoing colonoscopy, endoscopy, or surgery. * Develop new screening strategies based on substances found in tissue and biofluid samples. OUTLINE: This is a multicenter study. Patients and healthy volunteers undergo colonoscopy, endoscopy, or surgery. Patients and healthy volunteers also undergo tissue (e.g., tumor or normal mucosa) and biofluid (e.g., blood, urine, cyst fluids or tumor cells, bile and pancreatic juices, and/or stool) sample collection. Samples are analyzed for tumor markers by proteomic methods and protein analysis. If candidate biomarkers are identified, samples are stored for future studies involving these biomarkers. Information, including demographics, personal and family history of cancer, and prior and current colonoscopy, endoscopy, or surgery results, is collected from the medical record and stored in the project database. Patients are followed once a year for up to 5 years to determine if biomarkers have a prognostic significance.