Castle PE. SourceDivision of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA. castlep@mail.nih.gov Abstract Human papillomavirus (HPV) is the necessary but probably not sufficient cause of cervical precancer and cancer. Secondary exogenous and endogenous factors, HPV cofactors, may contribute to the probability of a cancer-associated (oncogenic) HPV infection progressing to cervical precancer and […]