Precancers can be dangerous because people with precancers are at a higher risk of developing cancer. Precancers are defined as abnormal lesions that occur before an invasive cancer appears, based on criteria developed by the National Cancer Institute's Conference on Precancer. Prevention and treatment of precancers can reduce the number of deaths caused by cancer.
If treated early, precancers can be prevented from developing into cancer. For example, the primary form of cervical begins with pre-cancerous changes in cervical cells. Physicians use the Pap smear and human papilloma virus (HPV) tests to screen women for precancers in the cervix. Any precancer found by these tests can be treated before the cervical cancer had a chance to fully develop.