[Eosinophilic esophagitis. Role of the pathologist in the diagnosis].

Eosinophilic esophagitis (EoE) is a chronic, immune-mediated esophageal disease with clinical symptoms and eosinophil-predominant inflammation. The diagnosis of EoE is therefore complex. It is not reflux or infectious or drug-induced. Histological cases with a high number of eosinophils are not a diagnostic problem. However, limits are of necessity in borderline cases. These must be based on the high power field (HPF) size and the percentage of squamous epithelium covering an HPF, which may greatly vary. Also, it must be considered that EoE is patchy in nature. In order to establish a reliable diagnosis a minimal number of biopsies is essential. Alongside the number of eosinophils further histological features associated with EoE, such as abcesses of eosinophils or basal layer enlargement, may be of diagnostic help in borderline cases.