Irregular Z-Line: To Biopsy or Not to Biopsy?

The z-line refers to the squamocolumnar junction which marks the transition between the normal stratified squamous epithelium of the distal esophagus and the columnar epithelium of the gastric cardia. An "irregular" z-line refers to an irregular appearing squamocolumnar junction characterized by the presence of columnar mucosa less than 1 cm in length that extends above the gastroesophageal junction. In contrast, Barrett's esophagus is diagnosed when columnar mucosa of at least 1 cm is seen in the distal esophagus extending above the gastroesophageal junction with biopsies demonstrating specialized intestinal metaplasia. Current guidelines recommend against taking routine biopsies from a normal or irregular z-line in the absence of visible abnormalities and advise against endoscopic surveillance in this patient population, in large part due to multiple studies demonstrating lack of progression to advanced neoplasia such as high-grade dysplasia or esophageal adenocarcinoma in patients with an irregular z-line. Despite these recommendations, a sizable number of patients without Barrett's esophagus undergo biopsies from the z-line and are subsequently recommended to have surveillance endoscopies. Furthermore, patients with an irregular z-line are often mislabelled as Barrett's esophagus resulting in significant downstream consequences including higher healthcare costs and reduced health-related quality of life. In this review, we highlight the importance of landmark identification of the distal esophagus and gastroesophageal junction at the time of endoscopy, share recommendations from current guidelines related to the z-line, examine rates of neoplastic progression in those with an irregular z-line, discuss consequences of routinely biopsying an irregular z-line, and highlight strategies on how to approach an irregular z-line if seen on endoscopy. A careful, high-quality endoscopic examination can help to identify visible abnormalities at the z-line, which, if present, should be targeted for biopsies to rule out dysplasia and neoplasia.