What Are CIN 1, CIN 2 and CIN 3?

Grades

CIN 1 (mild dysplasia / LSIL):

• Cell changes in the lower third of the epithelium
• A sign of active HPV infection
• Most regress spontaneously within 1–2 years
• Observation is preferred; treatment is rarely needed

CIN 2 (moderate dysplasia):

• Changes in two thirds of the epithelium
• Regression rate is lower
• Observation may be considered in women planning a pregnancy
• Excision (LEEP) is recommended for others

CIN 3 (severe dysplasia / carcinoma in situ):

• Changes throughout the full thickness of the epithelium
• Spontaneous regression is low
• Treatment is mandatory
• Excision (LEEP or conization) is preferred

In current terminology, CIN 2 and CIN 3 are also reported together as HSIL (high-grade squamous intraepithelial lesion). The pathology report should specify whether it is CIN 2 or CIN 3.

Natural history

In CIN 1, the regression rate within 2 years is about 60%, and progression to CIN 2+ is about 11%. In CIN 2, regression is 50–55% and progression about 19%. In CIN 3, regression is lower and treatment is recommended. HPV 16 and 18 positivity increases the risk of progression. Regression is higher in women under 30 and in HPV-negative cases. These rates are based on the meta-analyses by Tainio et al. (BMJ 2018) and Loopik et al. (2021).

Diagnosis

• Abnormal smear or high-risk HPV → colposcopy
• During colposcopy, abnormal areas are marked with acetic acid and Lugol’s solution
• A biopsy is taken from the suspicious area
• Pathology reports the CIN grade
• Endocervical curettage may be added when the transformation zone cannot be seen

Colposcopy is performed with the smear and HPV results known. If the biopsy shows CIN, management is planned accordingly.

Management (ASCCP 2019)

CIN 1:

• Observation is preferred
• Co-test (smear + HPV) after 1 year
• If it persists for 2 years, treatment options are discussed
• Observation during pregnancy

CIN 2:

• Treatment is recommended
• Observation is acceptable if pregnancy is planned and the transformation zone is visible
• Treatment is recommended if it persists for 2 years

CIN 3:

• Treatment is mandatory
• Observation is not acceptable
• LEEP or conization

Excision is preferred over ablation because it provides a specimen for pathology. Ablation (cryotherapy, laser) is considered only in selected, low-risk cases. Hysterectomy is not a primary treatment for CIN.

Follow-up after treatment

After treatment for CIN 2 or CIN 3, follow-up for at least 25 years is recommended: a co-test (smear + HPV) every year for the first 3 years, then every 3 years; at SoftCare, co-testing is preferred. After negative results, routine screening can be resumed. If there is a new partner or the risk changes, a reassessment is made.

Pregnancy

During pregnancy, CIN 1 is observed. In CIN 2 and CIN 3, colposcopic follow-up can be performed; at SoftCare, no biopsy is taken during pregnancy. Treatment is usually postponed until after delivery. If the risk of progression is low, observation is preferred.

Our approach at SoftCare

At SoftCare Clinic, an abnormal smear or HPV result is referred for colposcopy. If the biopsy shows CIN 1, observation is planned. For CIN 2 and CIN 3, LEEP is performed at SoftCare Clinic. If you are pregnant, management is adjusted accordingly. HPV 16/18 positivity and a history of previous high-grade lesions are taken into account in the risk assessment. Details are on the smear and colposcopy pages.

Appointments: +90 212 241 30 10 · softcareclinic.com

References

• 1. American Society for Colposcopy and Cervical Pathology (ASCCP). 2019 Risk-Based Management Consensus Guidelines for Abnormal Cervical Cancer Screening Tests and Cancer Precursors.
• 2. Perkins RB, Guido RS, Castle PE, et al. 2019 ASCCP Risk-Based Management Consensus Guidelines. J Low Genit Tract Dis. 2020;24(2):102–131.
• 3. UpToDate. Cervical intraepithelial neoplasia: Management.
• 4. Tainio K, Athanasiou A, Tikkinen KAO, et al. Clinical course of untreated cervical intraepithelial neoplasia grade 2 under active surveillance: systematic review and meta-analysis. BMJ. 2018;360:k499.
• 5. Loopik DL, et al. The Natural History of Cervical Intraepithelial Neoplasia Grades 1, 2, and 3: A Systematic Review and Meta-analysis. J Low Genit Tract Dis. 2021.
• 6. American College of Obstetricians and Gynecologists (ACOG). Updated Guidelines for Management of Cervical Cancer Screening Abnormalities. Practice Advisory, 2020.
• 7. World Health Organization (WHO). WHO guidelines for screening and treatment of precancerous lesions for cervical cancer prevention.
• Note: Management decisions are updated by the physician according to current ASCCP guidelines and individual risk. This reference list is for information only.

A citation does not mean that SoftCare wrote that text.

Medically reviewed by Op. Dr. Şükrü Sanus, Obstetrician & Gynecologist · Last medical review: 2 October 2026