There have been many advances in the pathology of intestinal tumours since the publication of the Third Series Intestines Fascicle in 2003, but many of the foundations of intestinal tumour diagnosis remain tried and true. Tubular adenomas are still tubular adenomas, but better understanding of serrated polyps has been a key advance in the years since the publication of the Third Series volume. Additionally, developments in molecular biology of colorectal carcinoma have allowed for targeted therapy and refinements to our evaluation of Lynch syndrome, which was termed hereditary nonpolyposis colorectal carcinoma (HNPCC) in the past. Our understanding of other polyposis syndromes has similarly blossomed in the past 15 years. Neuroendocrine tumours have been reclassified in the 2010 World Health Organization classification of gastrointestinal tumours. The molecular basis of gastrointestinal stromal tumours of the intestines has been a subject of great interest as well. In producing this update, this group of authors has enjoyed working together in gathering images and information to update this edition of the Intestines atlas. In doing so, we stand on the shoulders of giants before us, namely Drs. Robert H. Riddell, Robert E. Petras, Geraint T. Williams, and Leslie H. Sobin. While many areas of intestinal tumour pathology are without controversy, the classification and nomenclature for appendiceal tumours remain a subject of debate, including among ourselves. We have attempted to offer information on the various divergent viewpoints where they exist for this topic and others. Our efforts have been synergistic, and we hope that readers will enjoy the many interesting illustrations that we were able to amass.

Pathologists play a particularly important role in the care of patients with persistent gastrointestinal symptoms, especially those who are immunosuppressed, suffer from immune-mediated conditions, or undergo treatment for malignancies. They must be able to focus on key features present in biopsy material in order to narrow the differential diagnosis and facilitate patient management. This atlas addresses these needs in a succinct and pragmatic fashion. It describes practical approaches to the diagnosis of inflammatory gastrointestinal disorders and provides helpful criteria to distinguish between newly recognized causes of esophagitis and gastritis.

This issue of Surgical Pathology Clinics, edited by Rhonda K. Yantiss, will focus on Gastrointestinal Pathology: Common Questions and Diagnostic Dilemmas. Topics in this issue include, but are not limited to: Other forms of esophagitis; Diagnosis and management of Barrett-related neoplasia in the modern era; Patterns of gastric injury; Practical approach to the flat duodenal biopsy specimen; Chronic colitis in biopsy samples; Mucosal biopsy following bone marrow transplantation; The many faces of medication-related injury in the GI tract; The differential diagnosis of acute colitis: Clues to a specific diagnosis; Problematic colorectal polyps; Persistent problems in colorectal cancer reporting; Emerging concepts in gastric neoplasia; Immunohistochemistry pitfalls; Molecular testing in the modern era, and Lymphoproliferative diseases of the gut.