General features of the gastrointestinal tract and evaluation of specimens derived from it -- The nonneoplastic esophagus -- The neoplastic esophagus -- The nonneoplastic stomach -- The neoplastic stomach -- The nonneoplastic small intestine -- Epithelial tumors of the small intestine -- Nonneoplastic diseases of the appendix -- The neoplastic appendix -- Motility disorders -- Inflammatory bowel disease -- Polyposis and hereditary cancer syndromes -- The nonneoplastic colon -- Epithelial neoplasms of the colon -- The nonneoplastic anus -- Neoplastic lesions of the anus -- Gastrointestinal neuroendocrine lesions -- Lymphoproliferative disorders of the gastrointestinal tract -- Mesenchymal tumors.