Cervical Cancer Basics

Cervical cancer usually begins with persistent infection by a high-risk type of human papillomavirus (HPV), particularly HPV-16 or HPV-18. HPV infection is common and often clears without treatment. Cancer risk rises when high-risk HPV remains in cervical cells long enough to disrupt normal control of cell growth. The cervix contains a transformation zone where glandular and squamous cells meet. This area is especially vulnerable to HPV-related cell changes. Persistent infection can produce cervical intraepithelial neoplasia (CIN), a spectrum of precancerous changes. CIN remains above the basement membrane; invasive cancer has crossed that boundary and can invade surrounding tissue or spread elsewhere. This slow progression creates a major opportunity for prevention. HPV vaccination reduces the risk of infection with vaccine-covered HPV types, but it does not remove an established infection or treat existing precancer. Screening remains necessary after vaccination because vaccination does not cover every cancer-causing HPV type and some people were exposed before vaccination.