Abnormal cervical tissue is described using categories of cervical intraepithelial neoplasia (CIN). Categories are CIN 1, CIN 2, and CIN 3; increasing number designates the thickness of cervical lining with abnormal cells. CIN 3 is considered precancerous.
Host immune response to the virus resolves most HPV lesions, especially genital condolymas and CIN 1 lesions. Neither of these is precancerous. This regression ocassionally occurs with CIN 2, but rarely occurs with CIN 3. If the CIN does not regress, high-grade squamous intraepithelial lesions (HSIL) develop. HSIL may progress to invasive carcinoma, typically in older individuals.