Gastrointestinal Biomarkers in Tissue and Biological Fluid Samples From Patients and Healthy Participants

RATIONALE: Studying samples of tissue, blood, urine, stool, and other biological fluids from patients with cancer and from healthy participants 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 healthy participants undergoing colonoscopy, endoscopy, or surgery.