Precancerous changes in cervical cells caused primarily by persistent infection with high-risk human papillomavirus (HPV). Classified as CIN 1 (mild), CIN 2 (moderate), or CIN 3 (severe/carcinoma in situ). Most cases of CIN 1 resolve spontaneously; CIN 2-3 require treatment to prevent progression to invasive cervical cancer.

• 1Pap smear (cytology screening)
• 2HPV DNA testing
• 3Colposcopy with biopsy
• 4Endocervical curettage
• 5Cone biopsy for definitive diagnosis
• 6Co-testing (Pap + HPV)

CIN 1 resolves spontaneously in 60% of cases within 2 years; only 1% progress to cancer. CIN 2 regresses in 40%, persists in 40%, progresses to CIN 3 in 20%. CIN 3 untreated has 30% risk of progression to invasive cancer over 30 years. Treatment of CIN 2-3 reduces cancer risk by 95%. Excisional procedures may slightly increase preterm delivery risk in future pregnancies. Regular follow-up essential after treatment due to 5-15% recurrence rate.

• HPV vaccination (ages 9-26, up to 45 if not previously vaccinated)
• Regular cervical cancer screening
• Smoking cessation
• Consistent condom use
• Limiting number of sexual partners
• Treatment of precancerous lesions