HPV and cervical cancer
Cervical cancer is cancer of the cervix, which is the lower, narrow part of the uterus that connects to the vagina.
The Human Papillomavirus (HPV) causes almost all cervical cancer cases (approximately 99%). HPV is a sexually transmitted disease that is spread through skin-to-skin contact. There are more than 100 different strains of HPV. Many cause warts in the genitals or mouth, but some cause cervical cancer. Those types that cause cancer are “high-risk” types. The most common “high-risk” strains, types 16 and 18, cause approximately 70% of all cervical cancers.
HPV is extremely common – it is estimated that 75% of sexually active adults will have come into contact with the virus at some point in their lives. Often, the body will clear the HPV infection, possibly without any symptoms whatsoever.
Natural History of Anogenital Human Papillomavirus Infection and Neoplasia. Mark Schiffman and Susanne Kruger KjaerJ Natl Cancer Inst Monogr (2003) 2003 (31)- 14-19.
Cervical cancer can occur when there is a persistent HPV infection without treatment. A persistent infection is when the body does not clear the infection. When this happens the cells in the cervix begin to change abnormally, which can cause pre-cancerous lesions and even cervical cancer if left untreated.
It takes, on average, about 15-20 years for an HPV infection to develop into invasive cervical cancer.
Fortunately, because cervical cancer takes many years to develop, cervical pre-cancer can be detected and treated to prevent the formation of cancer.
The natural history of cervical HPV infection- unresolved issues Ciaran B. J. Woodman, Stuart I. Collins & Lawrence S. Young Nature Reviews Cancer 7, 11-22 (January 2007)
There are different grades of pre-cancer, which is often referred to as cervical intraepithelial neoplasia (CIN).
CIN I represents only mild abnormal cell growth, called dysplasia.
CIN II is moderate dysplasia
CIN III severe dysplasia to carcinoma
Because cervical cancer develops over many years, it can be prevented through screening linked with timely treatment. There are many different screening methods, some of which are more common in the US and some which are used primarily or exclusively in low-resource areas of the world. Some of the tests used to detect cervical pre-cancer are pap tests (smears), which check for the presence of abnormal cells in your cervix, HPV DNA tests, which detect the virus in vaginal or cervical cells, and VIA, which uses vinegar to detect pre-cancers lesions. The HPV vaccine can prevent infection if it is administered before infection occurs. Condoms can also help protect against HPV infection, but since the virus is transmitted through skin-to-skin contact, condoms do not offer 100% protection.