Monolayer columnar epithelium is a characteristic epithelium consisting of a layer of prismatic cells and a few cup-shaped cells, mostly distributed on the mucosal surface of the GI tract, uterus, and fallopian tubes, with absorptive or secretory functions. The clinical diagnostic significance is as follows: 1. Stomach: When the monolayer columnar epithelium of the stomach replaces the normal compound squamous epithelium of the distal esophagus, it leads to columnar epithelialization of the lower esophagus and then Barrett’s esophagus, which usually has no obvious symptoms and must be confirmed by endoscopy and pathological biopsy. Monolayer columnar epithelial lesions in the stomach can easily lead to heterogeneous hyperplasia or intraepithelial neoplasia, which can lead to gastric cancer in serious cases. Therefore, if there is daily stomach discomfort, gastroscopy should be improved promptly; 2. Cervix: It mainly refers to the outward migration of columnar epithelium from the endocervical canal to the ectocervix, which is a common physiological phenomenon. If combined with inflammation, it will manifest as increased leucorrhea, which is sticky or purulent with blood, repeated lower abdominal back pain, and contact bleeding, which requires medical attention, gynecological ultrasound, cervical cytology, HPV, and cervical secretion testing for diagnosis and treatment according to the situation. It is generally recommended that people with chronic diseases of the stomach or irregular lifestyle should undergo gastroscopy once a year and pay attention to a healthy diet on a daily basis; women should pay attention to the hygiene of their sexual life and menstrual period, and it is recommended to undergo cervical pre-cancer screening once a year.