Normal cervical epithelium – Columnar epithelium
The columnar epithelium lines the endocervix. In the normal cervix, the columnar epithelium is just visible near the external os. It appears as a red patch at the centre of the cervix after the cervix is cleaned with normal saline.
The columnar epithelium becomes prominent after application of acetic acid and has a velvety, grainy surface appearance. The finger-like villi protruding into the endocervical canal and the multiple longitudinal folds (fissures) are characteristics of the epithelium but may not always be visible.
The columnar epithelium may become temporarily white after application of acetic acid but regains its red colour within a few seconds. The junction between the squamous epithelium and the columnar epithelium becomes very distinct after application of acetic acid. The columnar epithelium retains its red colour after application of Lugol’s iodine.
Prominent normal branching blood vessels are often seen on the columnar epithelium, because the epithelium is thin and transparent.
Microscopic features: The columnar epithelium comprises a single layer of columnar cells. The epithelium invaginates in the cervical stroma to form crypts.