Pathology of eosinophilic esophagitis: what the clinician needs to know

Eosinophilic esophagitis (EOE) is a clinical pathologic syndrome characterized by influx of numerous eosinophils into the esophageal epithelium. It is important for clinicians to be aware of the spectrum, as well as the characteristic location and distribution, of morphologic changes in EOE to maximize the diagnostic yield in mucosal biopsy specimens. The major pathologic features of EOE include eosinophilic microabscesses, surface layering of eosinophils often associated with surface sloughing of necrotic squamous cells, and peak eosinophil counts usually greater than 15 per high power field (hpf) within the squamous epithelium. Minor features, which are frequent but less specific, include marked basal cell hyperplasia, lengthening of lamina propria papillae, intercellular edema, and lamina propria fibrosis with chronic inflammation. The number, distribution, and location of intraepithelial eosinophils in EOE vary greatly between previously published studies. Thus, utilization of a diagnostic cutoff point for intraepithelial eosinophils in EOE, particularly in the absence of other major features of EOE, is currently considered unwise. In fact, some patients may show combined features of both gastroesophageal reflux disease (GERD) and EOE, which complicates the histologic analysis of these patients. In contrast to GERD, EOE typically involves longer lengths of the esophagus, affects the proximal equally, or even more, than the distal esophagus, and the pathologic findings are often patchy in distribution. As a result, it is highly recommended that clinicians obtain biopsies from patients suspected of have EOE only after treatment with high-dose proton pump inhibitor therapy, and that biopsies be obtained from both the proximal and distal esophagus in both normal and abnormal appearing areas.