Acquired ectropion and formation of the transformation zone
Acquired cervical ectopia is formed as a result of the epithelization of true erosion. Columnar epithelium appears on the surface of the exocervix, originating from reserve cells. Hormonal disorders and urogenital infections, including viral ones, contribute to the development of this process.
Clinically, ectopia is most often asymptomatic. However, when accompanied by concomitant exo- or endocervicitis, patients may complain of leukorrhea and contact spotting. On speculum examination, ectopia appears as an irregular, asymmetrical bright-red area against the background of a pale mucous membrane. The colposcopic picture demonstrates a velvety surface consisting of multiple red papillae. The specific color is due to the blood vessels of the underlying stroma shining through the single layer of columnar cells.
Transformation zone (TZ) is the area where columnar epithelium is replaced by stratified squamous epithelium. During colposcopy, immature and metaplastic squamous epithelium is visualized here. A characteristic feature of the TZ is open and closed glandular ducts, which form when squamous epithelium covers crypts in the area of ectopia.
Papillomavirus infection and its effect on the epithelium
Human papillomavirus (HPV) has a pronounced tropism for epithelial cells. The infection is extremely common: up to 80% of the sexually active population encounters it, and transmission often goes unnoticed.
Low- and high-oncogenic-risk serotypes are distinguished. High-oncogenic types include 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, and 58. Serotypes 16 and 18 are the most dangerous — they are responsible for approximately 80% of cases of high-grade dysplasia and cervical cancer.
HPV is a DNA-containing virus. Its structural proteins are encoded by the L1 and L2 genes, while functional proteins are encoded by the remaining genes, among which E6 and E7 are responsible for tumor transformation. The virus goes through two stages in the cell:
- Episomal — viral particles are assembled inside the epitheliocyte (productive effect leading to the formation of papillomas).
- Integrative — viral DNA is integrated into the cell genome, initiating a transforming effect (development of dysplasia and cancer).
Spontaneous viral elimination occurs in 95% of infected individuals within 9–15 months. Persistence is observed in only 5% of patients (against the background of antitumor defense defects) and leads to the development of cancer within 2–15 years. Diagnostics is based on PCR, microscopy (detection of koilocytosis), and solution hybridization (Digene test). Serodiagnosis is not used, as antibodies are formed in less than 30% of patients.
Cervical intraepithelial neoplasia (CIN) and management tactics
Cervical dysplasia (CIN) is a process of cellular and structural atypia with impaired differentiation and stratification of the epithelium. The key morphological criterion is absence of basement membrane involvement. Microscopy reveals cellular polymorphism, an increased number of mitoses, and nuclear karyorrhexis / dyskaryosis.
According to the WHO classification, three degrees of lesion are distinguished:
- Mild dysplasia (CIN I): atypia is limited to the lower third of the epithelial layer.
- Moderate dysplasia (CIN II): changes involve the lower and middle thirds.
- Severe dysplasia (CIN III): the entire layer of stratified squamous epithelium is affected.
Dysplasia is asymptomatic, so screening is the basis for detection: mandatory cytological smear examination and colposcopy.
Treatment tactics depend on the clinical picture. Uncomplicated ectopia in nulliparous women requires only dynamic observation. In case of persistent inflammation and HPV, conservative treatment is performed first, followed by surgical treatment (cryodestruction, laser coagulation).
The main method of surgical intervention for pathology of the transformation zone is its loop electrosurgical excision, followed by curettage of the cervical canal and pathomorphological examination of the material. Targeted biopsy is acceptable in young patients (if the TZ is fully visualized and there are no signs of invasion). Cone excision (conization) is indicated for women over 50 or with a type 3 transformation zone.
To remember the stages of dysplasia (CIN), imagine a multi-story building: CIN I — renovation only on the first floor (lower third of the layer), CIN II — the first and second floors are affected (lower and middle thirds), CIN III — remodeling of the entire building (the entire epithelial layer), but the foundation itself (basement membrane) is still intact.
Class and exam questions
Why does ectopia appear bright red on examination?
Columnar epithelium consists of just a single layer of cells. Blood vessels of the underlying stroma shine clearly through it, which produces the characteristic color against the pale exocervix.
What is the difference between the episomal and integrative stages of HPV?
In the episomal stage, the virus assembles its particles inside the cell, causing the formation of papillomas. In the integrative stage, the viral DNA integrates into the epitheliocyte genome, triggering the process of tumor transformation.
Is it always necessary to cauterize ectopia?
No. In nulliparous women with uncomplicated ectopia, only dynamic observation is indicated. Surgical treatment is required in the presence of persistent inflammation and HPV.
What else to study on this topic
- Colposcopic signs of invasion and assessment of transformation zone types.
- Morphological differences of koilocytosis in subclinical HPV infection.
- Mechanisms of action of human papillomavirus E6 and E7 oncoproteins.
- Indications for radiosurgical intervention and laser coagulation.
- Histological picture of exo- and endocervicitis.
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