CIN1 lesions usually subside on their own (in 80-90% of cases) within 2-3 years after the biopsies and diagnosis. This is why the term «intraepithelial neoplasia» is considered an exaggeration. It is believed that this kind of cell atypia is due to simple infection from HPV (infectious atypia). This is why CIN1 lesions are classified as LSIL (low-grade lesions).
On the contrary, CIN2 and CIN3 lesions have a significant possibility of evolving into invasive cancer in the following years. This is why they are classified as HSIL (high-grade lesions). If CIN2/3 or HSIL lesions aren’t treated, there is a future risk of invasive cancer. The risk is estimated at 30-40% of all cases, but is lower at younger ages and higher after the age of 30. The risk for carcinogenesis (development of cancer) increases with age.
CIN3 lesions have a higher risk for invasive cancer. Especially in regard to CIN3 and CIS lesions, the lifetime risk is estimated at 60-80%. Women older than 30, with CIN3/CIS lesions covering a large part of the cervical surface, are at the highest risk.