Histopathologic Diagnosis of Eosinophilic Conditions in the Gastrointestinal TractHurrell, Jennifer M. DO*; Genta, Robert M. MD*,†; Melton, Shelby D. MD*Advances in Anatomic Pathology: September 2011 - Volume 18 - Issue 5 - p 335–348 doi: 10.1097/PAP.0b013e318229bfe2 Review Articles Abstract Author Information Eosinophils, a constitutive component of the columnar-lined gastrointestinal tract, play an essential role in allergic responses and parasitic infections. The tissue density of these cells also increases in a variety of conditions of uncertain etiology. With the exception of the esophageal squamous epithelium, in which no eosinophils are normally present, the population of normal eosinophils in the remainder of the luminal gut is poorly defined. Therefore, histopathologists must rely on their subjective judgment to determine when a diagnosis of eosinophilic gastritis, enteritis, or colitis should be rendered. Eosinophilic esophagitis is currently the best defined and most studied eosinophilic condition of the digestive tract; therefore, the confidence in accurate diagnosis is increasing. In contrast, the characteristic clinicopathologic features of eosinophilic conditions affecting other parts of the digestive tract remain somewhat elusive. This review was designed to present pathologists with simple and practical information for the biopsy-based histopathologic diagnosis of eosinophilic esophagitis, gastritis, enteritis, and colitis. It was prepared by critically reviewing more than 200 articles on the topic, along with incorporating evidence accumulated through our own collective experience. We anticipate that by increasing pathologists' confidence in reporting these abnormal but often nameless eosinophilic infiltrates, we can help better define and characterize their significance. *Department of Pathology, VA North Texas Health Care System and University of Texas Southwestern Medical Center, Dallas †Caris Research Institute, Caris Life Sciences, Irving, TX The authors have no funding or conflicts of interest to disclose. Reprints: Shelby D. Melton, MD, VA North Texas Health Care System, Pathology and Laboratory Medicine Service (113), Dallas, TX 75216 (e-mail: firstname.lastname@example.org). © 2011 Lippincott Williams & Wilkins, Inc.