Cervical Intraepithelial Neoplasia (CIN)
NHS England guidance NHS cervical screening (CSP) programme. Cervical screening care pathway. Last updated: Jul 2025.
NHS England Guidance Cervical screening: programme and colposcopy management. Last updated: Jul 2025.
Cervical Intraepithelial Neoplasia (CIN)
Cervical intraepithelial neoplasia (CIN) is a pre-cancerous condition in which dysplastic cells are confined to the cervical epithelium and have not breached the basement membrane. It is usually asymptomatic and is detected through cervical screening or colposcopic biopsy rather than clinical presentation.
Updated UKMLA guide to cervical intraepithelial neoplasia (CIN): definition, classification, and management, based on the NHS cervical screening programme.
Definition
CIN is a pre-cancerous (pre-invasive) condition, where abnormal (dysplastic) cells are present within the cervical epithelium that have NOT invaded through the basement membrane (thus “intraepithelial”).
CIN is different from cervical cancer, which is technically termed invasive cervical carcinoma. Cervical cancer is characterised by malignant cervical cells that have breached the basement membrane and invaded the underlying cervical stroma.
Classification
CIN can be classified into 3 grades based on histological findings, primarily according to the proportion of the epithelium involved by dysplastic cells
- CIN I = lower 1/3 of epithelium
- CIN 2 = lower 2/3 of epithelium
- CIN 3 = > lower 2/3 to full thickness of epithelium
Clinical Features
CIN is asymptomatic; it can only be detected via cervical screening (see the Cervical Cancer article).
Management
Management depends on the CIN grade:
| CIN grade | Typical management | Follow-up |
|---|---|---|
| 1 | Active observation (conservative management) | Perform a follow-up hrHPV testing
|
| 2* | Immediate treatment
Standard approach: excisional techniques (conisation / cone biopsy e.g. LLETZ) |
Perform hrHPV testing at 6 months post-treatment |
| 3 |
*Certain patients with CIN 2 can undergo active observation (conservative management) as an alternative to immediate treatment, but only if they meet very specific safety criteria (e.g. small lesion, MDT approval, committing to strict 6-monthly check-ups)
Disclaimer:
The table above only covers when follow-up hrHPV testing should be performed. Management based on follow-up test results is omitted, as it is unlikely that one would be expected to learn all subsequent steps.