Clinical overview
Most of what a registrar sees on the cervix in a busy South African gynaecology or family-planning clinic is benign. Ectropion, polyps, Nabothian cysts, cervicitis and benign metaplasia together account for the great majority of "abnormal-looking" cervices, abnormal discharge, and post-coital or intermenstrual bleeding referred for colposcopy. The pathophysiology of these conditions is, at root, the physiology of the cervix itself — the dynamic remodelling of the transformation zone under oestrogen, the response of columnar epithelium to a low vaginal pH, and the reaction of cervical stroma and glands to mechanical and infective insult. Understanding that physiology is what lets you confidently reassure most women, while never missing the cancer hiding behind an identical clinical picture.
The exam-relevant tension is precisely that overlap. Cervical ectropion and an early invasive carcinoma can both present as a friable, contact-bleeding cervix; a benign endocervical polyp and an early endometrial or cervical neoplasm can both present as intermenstrual bleeding. In a country with one of the highest cervical-cancer burdens in the world — driven by very high HIV prevalence and historically patchy screening coverage — the discipline is to treat benign cervical disease as a diagnosis of exclusion that is reached through the screening and colposcopic pathway, not around it. This chapter describes the pathophysiology of the common benign lesions and frames them firmly inside the South African screening reality and the WHO 90-70-90 elimination agenda.
Core knowledge
The transformation zone — the engine of benign cervical change
The ectocervix is lined by non-keratinised stratified squamous epithelium continuous with the vagina; the endocervical canal is lined by a single layer of mucin-secreting columnar epithelium thrown into deep clefts and crypts (often loosely called "glands", though they are infoldings rather than true acini). The junction between them — the squamocolumnar junction (SCJ) — is not fixed. Its position migrates over a woman's life under hormonal control, and the band of epithelium between the original SCJ and the current SCJ is the transformation zone (TZ).
Two processes drive almost all benign (and indeed neoplastic) cervical change in the TZ:
- Eversion (ectropion). Under high oestrogen states — puberty, the reproductive years, pregnancy, and combined oral contraceptive use — the cervix grows and the canal everts, exposing the soft red columnar epithelium onto the ectocervix.
- Squamous metaplasia. Once columnar epithelium is exposed to the acidic vaginal environment (pH ~3.5–4.5, maintained by lactobacilli), the relatively fragile single-cell layer is progressively replaced by more robust squamous epithelium. This is a normal, physiological, protective adaptation — metaplasia, not dysplasia. It begins with reserve-cell hyperplasia beneath the columnar cells, which then differentiate into immature and finally mature squamous epithelium.
The metaplastic TZ is biologically the most important real estate in gynaecological oncology: it is the actively dividing, susceptible epithelium where high-risk HPV establishes persistent infection and where essentially all squamous cervical neoplasia arises (see Cervical carcinogenesis and HPV pathology). The same physiology that produces benign metaplasia is the substrate for malignant transformation — which is exactly why benign and pre-malignant disease share a clinical appearance.
Cervical ectropion (ectopy)
Figure D6.1 — Cervical ectropion/ectopy: hormone-driven eversion of columnar epithelium onto the ectocervix — normal physiology that mimics cancer.
Ectropion is the visible presence of endocervical columnar epithelium on the ectocervix. It is not a disease, an erosion, or a pre-malignant condition — the older term "cervical erosion" is a misnomer because nothing is eroded; the epithelium is simply everted and exposed. Macroscopically it appears as a well-demarcated red, sometimes granular or "strawberry" zone around the external os, contrasting with the pale pink squamous ectocervix.
The columnar epithelium is a single cell thick over a rich subepithelial capillary network, which explains the two cardinal features:
- Friability and contact bleeding — the thin epithelium is easily traumatised (intercourse, speculum, swab), producing post-coital or contact bleeding.
- Increased mucoid discharge — exposed mucin-secreting columnar cells produce more clear/mucoid discharge than squamous epithelium would.
Drivers are the high-oestrogen states listed above; ectropion is therefore common in adolescents, pregnant women, and combined-pill users, and tends to regress after menopause as oestrogen falls and the SCJ recedes into the canal. Histologically there is normal columnar (or partly metaplastic) epithelium with no atypia. The clinical importance is entirely in its mimicry: a friable, bleeding cervix is also the presentation of cervicitis, of HPV-related disease, and of early invasive carcinoma. Ectropion is a diagnosis of exclusion made after malignancy has been ruled out by appropriate screening/colposcopy.