[Lymphocytic "…itis", from esophagus to large bowel]

Intra-epithelial lymphocytosis is an elementary lesion frequently observed in the gastrointestinal tract, which can be found from the esophagus to the colon. Many conditions of a varied nature (dysimmunitary diseases, drugs, infections…) are associated with intra-epithelial lymphocytosis, and the etiological diagnosis most often requires an anatomo-clinical correlation. The pathologist will have to identify histological lesions associated with intra-epithelial lymphocytosis allowing the diagnosis to be oriented in order to propose appropriate treatment. In this review, the main entities associated with digestive intra-epithelial lymphocytosis will be presented, detailing the key elements allowing their diagnosis.