Molecular Basis of Diseases of the Gastrointestinal Tract

Much of the progress in the understanding of gastrointestinal disorders has continued to center on the molecular underpinning of gastrointestinal neoplasia in the 21st century. First, the development of cancer in the setting of inflammatory conditions is well represented by the association of Helicobacter pylori with gastric cancer and of inflammatory bowel diseases with colorectal cancer. Second, the development of cancer in patients with hereditary predisposition syndromes has shed light not only in the mechanisms of hereditary neoplasia, but has also led to major progress in the understanding of the molecular basis of the more common forms of sporadic cancer. The molecular characterization of the steps of gastrointestinal neoplastic development and progression has led to advances in disease diagnosis and treatment and has opened the opportunity for development of more targeted approaches to cancer prevention, surveillance, and novel therapeutics. This chapter focuses on the disease processes that most clearly illustrate the concepts and advances in molecular pathology of the gastrointestinal tract. It includes neoplastic diseases associated with a background of chronic inflammation, well-characterized gastrointestinal hereditary cancer syndromes, and the so-called sporadic cancers of the gastrointestinal tract, primarily reviewing gastric and colonic carcinogenesis.