Cervical cancer

Cervical cancer is malignant neoplasm of the cervix uteri or cervical area. One of the most common symptoms is abnormal vaginal bleeding, but in some cases there may be no obvious symptoms until the cancer is in its advanced stages. Treatment consists of surgery (including local excision) in early stages and chemotherapy and radiotherapy in advanced stages of the disease.

Pap smear screening can identify potentially precancerous changes. Treatment of high grade changes can prevent the development of cancer. In developed countries, the widespread use of cervical screening programs has reduced the incidence of invasive cervical cancer by 50% or more.

Human papillomavirus (HPV) infection is a necessary factor in the development of almost all cases of cervical cancer. HPV vaccines effective against the two strains of HPV that currently cause approximately 70% of cervical cancer have been licensed in the U.S, Canada, Australia and the EU. Since the vaccines only cover some of the cancer causing ("high-risk") types of HPV, women should seek regular Pap smear screening, even after vaccination.



The cervix is the narrow portion of the uterus where it joins with the top of the vagina. Most cervical cancers are squamous cell carcinomas, arising in the squamous (flattened) epithelial cells that line the cervix. Adenocarcinoma, arising in glandular epithelial cells is the second most common type. Very rarely, cancer can arise in other types of cells in the cervix.

Signs and symptoms
The early stages of cervical cancer may be completely asymptomatic. Vaginal bleeding, contact bleeding or (rarely) a vaginal mass may indicate the presence of malignancy. Also, moderate pain during sexual intercourse and vaginal discharge are symptoms of cervical cancer. In advanced disease, metastases may be present in the abdomen, lungs or elsewhere.

Symptoms of advanced cervical cancer may include: loss of appetite, weight loss, fatigue, pelvic pain, back pain, leg pain, single swollen leg, heavy bleeding from the vagina, leaking of urine or faeces from the vagina, and bone fractures.

Causes
Human papillomavirus (HPV) infection with high-risk types has been shown to be a necessary factor in the development of cervical cancer. HPV DNA may be detected in virtually all cases of cervical cancer. Not all of the causes of cervical cancer are known. Several other contributing factors have been implicated.

Human papillomavirus infection
In the United States each year there are more than 6.2 million new HPV infections in both men and women, according to the CDC, of which 10 percent will go on to develop persistent dysplasia or cervical cancer. That is why HPV is known as the "common cold" of the sexually transmitted infection world. It is very common and affects roughly 80 percent of all sexually active people, whether they have symptoms or not. The most important risk factor in the development of cervical cancer is infection with a high-risk strain of human papillomavirus. The virus cancer link works by triggering alterations in the cells of the cervix, which can lead to the development of cervical intraepithelial neoplasia, which can lead to cancer.

Women who have many sexual partners (or who have sex with men who had many other partners) have a greater risk.

More than 150 types of HPV are acknowledged to exist (some sources indicate more than 200 subtypes). Of these, 15 are classified as high-risk types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73, and 82), 3 as probable high-risk (26, 53, and 66), and 12 as low-risk (6, 11, 40, 42, 43, 44, 54, 61, 70, 72, 81, and CP6108). Types 16 and 18 are generally acknowledged to cause about 70% of cervical cancer cases. Together with type 31, they are the prime risk factors for cervical cancer.

Genital warts are caused by various strains of HPV which are usually not related to cervical cancer. However, it is possible to have multiple strains at the same time, including those that can cause cervical cancer along with those that cause warts. The medically accepted paradigm, officially endorsed by the American Cancer Society and other organizations, is that a patient must have been infected with HPV to develop cervical cancer, and is hence viewed as a sexually transmitted disease (although many dispute that, technically, it is the causative agent, not the cancer, that is a sexually transmitted disease), but most women infected with high risk HPV will not develop cervical cancer. Use of condoms reduces, but does not always prevent transmission. Likewise, HPV can be transmitted by skin-to-skin-contact with infected areas. In males, there is no commercially available test for HPV, although HPV is thought to grow preferentially in the epithelium of the glans penis, and cleaning of this area may be preventative.

Cofactors
The American Cancer Society provides the following list of risk factors for cervical cancer: human papillomavirus (HPV) infection, smoking, HIV infection, chlamydia infection, stress and stress-related disorders, dietary factors, hormonal contraception, multiple pregnancies, exposure to the hormonal drug diethylstilbestrol, and family history of cervical cancer. Early age at first intercourse and first pregnancy are also considered risk factors, magnified by early use of oral contraceptives. There is a possible genetic risk associated with HLA-B7.

There has not been any definitive evidence to support the claim that circumcision of the male partner reduces the risk of cervical cancer, although some researchers say there is compelling epidemiological evidence that men who have been circumcised are less likely to be infected with HPV. However, in men with low-risk sexual behaviour and monogamous female partners, circumcision makes no difference to the risk of cervical cancer.

Biopsy procedures
While the pap smear is an effective screening test, confirmation of the diagnosis of cervical cancer or pre-cancer requires a biopsy of the cervix. This is often done through colposcopy, a magnified visual inspection of the cervix aided by using a dilute acetic acid (e.g. vinegar) solution to highlight abnormal cells on the surface of the cervix.

Colposcopic impression, the estimate of disease severity based on the visual inspection, forms part of the diagnosis.

Further diagnostic and treatment procedures are loop electrical excision procedure (LEEP) and conization, in which the inner lining of the cervix is removed to be examined pathologically. These are carried out if the biopsy confirms severe cervical intraepithelial neoplasia.



Precancerous lesions
Cervical intraepithelial neoplasia, the potential precursor to cervical cancer, is often diagnosed on examination of cervical biopsies by a pathologist. For premalignant dysplastic changes, the CIN (cervical intraepithelial neoplasia) grading is used.

The naming and histologic classification of cervical carcinoma percursor lesions has changed many times over the 20th century. The World Health Organization classification system was descriptive of the lesions, naming them mild, moderate or severe dysplasia or carcinoma in situ (CIS). The term, Cervical Intraepithelial Neoplasia (CIN) was developed to place emphasis on the spectrum of abnormality in these lesions, and to help standardise treatment. It classifies mild dysplasia as CIN1, moderate dysplasia as CIN2, and severe dysplasia and CIS as CIN3. More recently, CIN2 and CIN3 have been combined into CIN2/3. These results are what a pathologist might report from a biopsy.

These should not be confused with the Bethesda System terms for Pap smear (cytopathology) results. Among the Bethesda results: Low-grade Squamous Intraepithelial Lesion (LSIL) and High-grade Squamous Intraepithelial Lesion (HSIL). An LSIL Pap may correspond to CIN1, and HSIL may correspond to CIN2 and CIN3, however they are results of different tests, and the Pap smear results need not match the histologic findings.

Cancer subtypes
Histologic subtypes of invasive cervical carcinoma include the following:  Though squamous cell carcinoma is the cervical cancer with the most incidence, the incidence of adenocarcinoma of the cervix has been increasing in recent decades.
 * squamous cell carcinoma (about 80-85%)
 * adenocarcinoma (about 15% of cervical cancers in the UK )
 * adenosquamous carcinoma
 * small cell carcinoma
 * neuroendocrine tumour
 * glassy cell carcinoma
 * villoglandular adenocarcinoma

Non-carcinoma malignancies which can rarely occur in the cervix include
 * melanoma
 * lymphoma

Note that the FIGO stage does not incorporate lymph node involvement in contrast to the TNM staging for most other cancers.

For cases treated surgically, information obtained from the pathologist can be used in assigning a separate pathologic stage but is not to replace the original clinical stage.

Staging
Cervical cancer is staged by the International Federation of Gynecology and Obstetrics (FIGO) staging system, which is based on clinical examination, rather than surgical findings. It allows only the following diagnostic tests to be used in determining the stage: palpation, inspection, colposcopy, endocervical curettage, hysteroscopy, cystoscopy, proctoscopy, intravenous urography, and X-ray examination of the lungs and skeleton, and cervical conization.

be disregarded)
 * Stage I	The carcinoma is strictly confined to the cervix (extension to the corpus would
 * IA	Invasive carcinoma which can be diagnosed only by microscopy, with deepest

invasion <5 mm and the largest extension >7 mm


 * IA1	Measured stromal invasion of <3.0 mm in depth and extension of <7.0 mm


 * IA2	Measured stromal invasion of >3.0 mm and not >5.0 mm with an extension of

not >7.0 mm
 * IB	Clinically visible lesions limited to the cervix uteri or pre-clinical cancers

greater than stage IA


 * IB1	Clinically visible lesion <4.0 cm in greatest dimension


 * IB2	Clinically visible lesion >4.0 cm in greatest dimension


 * Stage II	Cervical carcinoma invades beyond the uterus, but not to the pelvic wall or to the lower third of the vagina


 * IIA	Without parametrial invasion
 * IIA1	Clinically visible lesion <4.0 cm in greatest dimension


 * IIA2	Clinically visible lesion >4.0 cm in greatest dimension


 * IIB	With obvious parametrial invasion


 * Stage III	The tumour extends to the pelvic wall and/or involves lower third of the vagina and/or causes hydronephrosis or non-functioning kidney


 * IIIA	Tumour involves lower third of the vagina, with no extension to the pelvic wall


 * IIIB	Extension to the pelvic wall and/or hydronephrosis or non-functioning kidney


 * Stage IV	The carcinoma has extended beyond the true pelvis or has involved (biopsy proven) the mucosa of the bladder or rectum. A bullous oedema, as such, does not permit a case to be allotted to Stage IV
 * IVA	Spread of the growth to adjacent organs
 * IVB	Spread to distant organs

Stage 1-A1 young women - conization wis clear margin. Parous women - hysterectomy.

Stage 1-A2 laproscopic lymphadenectomy + vaginal trechelectomy + post operative radiotherapy.

Stage 1B & 2A 1. Wertheim's hysterectomy. 2- schauta vaginal hysterectomy + laparoscopic lymphadenectomy 3: primary radiotherapy 4: combined surgery & radiotherapy.

Stage 2B, 3, 4 -  chemotherapy

Vaccination
Gardasil, is a vaccine against HPV types 6, 11, 16 & 18 which is up to 98% effective.

Cervarix has been shown to be 92% effective in preventing HPV strains 16 and 18 and is effective for more than four years.

Together, HPV types 16 and 18 currently cause about 70% of cervical cancer cases. HPV types 6 and 11 cause about 90% of genital wart cases. HPV vaccines have also been shown to prevent precursors to some other cancers associated with HPV.

HPV vaccines are targeted at girls and women of age 9 to 26 because the vaccine only works if given before infection occurs; therefore, public health workers are targeting girls before they begin having sex. The vaccines have been shown to be effective for at least 4 to 6 years, and it is believed they will be effective for longer, however the duration of effectiveness and whether a booster will be needed is unknown.

The use of the vaccine in men to prevent genital warts, anal cancer, and interrupt transmission to women or other men is initially considered only a secondary market.

The high cost of this vaccine has been a cause for concern. Several countries have or are considering programs to fund HPV vaccination.

Condoms
Condoms offer some protection against cervical cancer. Evidence on whether condoms protect against HPV infection is mixed, but they may protect against genital warts and the precursors to cervical cancer. They also provide protection against other STDs, such as HIV and Chlamydia, which are associated with greater risks of developing cervical cancer.

Condoms may also be useful in treating potentially precancerous changes in the cervix. Exposure to semen appears to increase the risk of precancerous changes (CIN 3), and use of condoms helps to cause these changes to regress and helps clear HPV. One study suggests that prostaglandin in semen may fuel the growth of cervical and uterine tumours and that affected women may benefit from the use of condoms.

Smoking
Carcinogens from tobacco increase the risk for many cancer types, including cervical cancer, and women who smoke have about double the chance of a nonsmoker to develop cervical cancer.

Nutrition
Higher levels of vegetable consumption were associated with a 54% decrease risk of HPV persistence.
 * Fruits and vegetables

There is weak evidence to suggest a significant deficiency of retinol can increase chances of cervical dysplasia, independently of HPV infection. A small (n~=500) case-control study of a narrow ethnic group (native Americans in New Mexico) assessed serum micro-nutrients as risk factors for cervical dysplasia. Subjects in the lowest serum retinol quartile were at increased risk of CIN I compared with women in the highest quartile.
 * Vitamin A

However, the study population had low overall serum retinol, suggesting deficiency. A study of serum retinol in a well-nourished population reveals that the bottom 20% had serum retinol close to that of the highest levels in this New Mexico sub-population.

Risk of type-specific, persistent HPV infection was lower among women reporting intake values of vitamin C in the upper quartile compared with those reporting intake in the lowest quartile.
 * Vitamin C

HPV clearance time was significantly shorter among women with the highest compared with the lowest serum levels of tocopherols, but significant trends in these associations were limited to infections lasting 120 days) was not significantly associated with circulating levels of tocopherols. Results from this investigation support an association of micronutrients with the rapid clearance of incident oncogenic HPV infection of the uterine cervix.
 * Vitamin E

A statistically significantly lower level of alpha-tocopherol was observed in the blood serum of HPV-positive patients with cervical intraepithelial neoplasia. The risk of dysplasia was four times higher for an alpha-tocopherol level < 7.95 mumol/l.

Higher folate status was inversely associated with becoming HPV test-positive. Women with higher folate status were significantly less likely to be repeatedly HPV test-positive and more likely to become test-negative. Studies have shown that lower levels of antioxidants coexisting with low levels of folic acid increases the risk of CIN development. Improving folate status in subjects at risk of getting infected or already infected with high-risk HPV may have a beneficial impact in the prevention of cervical cancer.
 * Folic acid

However, another study showed no relationship between folate status and cervical dysplasia.

The likelihood of clearing an oncogenic HPV infection is significantly higher with increasing levels of lycopenes. A 56% reduction in HPV persistence risk was observed in women with the highest plasma [lycopene] concentrations compared with women with the lowest plasma lycopene concentrations. These data suggests that vegetable consumption and circulating lycopene may be protective against HPV persistence.
 * Carotenoids

Screening
The widespread introduction of the Papanicolaou test, or Pap smear for cervical cancer screening has been credited with dramatically reducing the incidence and mortality of cervical cancer in developed countries. Pap smear screening every 3–5 years with appropriate follow-up can reduce cervical cancer incidence by up to 80%. Abnormal Pap smear results may suggest the presence of cervical intraepithelial neoplasia (potentially premalignant changes in the cervix) before a cancer has developed, allowing examination and possible preventive treatment. If premalignant disease or cervical cancer is detected early, it can be monitored or treated relatively noninvasively, with little impairment of fertility.

Cervical cancer screening is typically recommended starting three years or more after first sex, or starting at age 21 to 25. Recommendations for how often a Pap smear should be done vary from once a year to once every five years, in the absence of abnormal results. Guidelines vary on how long to continue screening, but well screened women who have not had abnormal smears can stop screening about age 60 to 70.

To take a Pap smear, the vagina is held open with a speculum, the loose surface cells on the cervix are scraped using a specially shaped spatula and a brush, and the cells are spread on a microscope slide. At a laboratory the slide is stained, examined for abnormal cells and findings are reported.

Until recently the Pap smear has remained the principal technology for preventing cervical cancer. However, following a rapid review of the published literature, originally commissioned by NICE, liquid based cytology has been incorporated within the UK national screening programme. Although it was probably intended to improve on the accuracy of the Pap test, its main advantage has been to reduce the number of inadequate smears from around 9% to around 1%. This reduces the need to recall women for a further smear.

Automated technologies have been developed with the aim of improving on the interpretation of smears, normally carried out by cytotechnologists. Unfortunately these on the whole have proven less useful; although the more recent reviews suggest that generally they may be no worse than human interpretation.

The HPV test is a newer technique for cervical cancer triage which detects the presence of human papillomavirus infection in the cervix. It is more sensitive than the pap smear (less likely to produce false negative results), but less specific (more likely to produce false positive results) and its role in routine screening is still evolving. Since more than 99% of invasive cervical cancers worldwide contain HPV, some researchers recommend that HPV testing be done together with routine cervical screening. But, given the prevalence of HPV (around 80% infection history among the sexually active population) others suggest that routine HPV testing would cause undue alarm to carriers, more unnecessary follow-up testing and treatment. HPV testing along with cytology significantly increases the cost of screening.

VIA/cryo, for visualization of the cervix with acetic acid (vinegar) and treatment with cryotherapy, sometimes with special lights (speculoscopy), or taking pictures for expert evaluation (cervicography) have been evaluated as adjuncts to or replacements for Pap smear screening, especially in countries where Pap smear screening is prohibatively expensive. There are efforts to develop low cost HPV tests which might be used for primary screening of older women in less developed countries.

Treatment
Microinvasive cancer (stage IA) is usually treated by hysterectomy (removal of the whole uterus including part of the vagina). For stage IA2, the lymph nodes are removed as well. An alternative for patients who desire to remain fertile is a local surgical procedure such as a loop electrical excision procedure (LEEP) or cone biopsy.

If a cone biopsy does not produce clear margins, one more possible treatment option for patients who want to preserve their fertility is a trachelectomy. This attempts to surgically remove the cancer while preserving the ovaries and uterus, providing for a more conservative operation than a hysterectomy. It is a viable option for those in stage I cervical cancer which has not spread; however, it is not yet considered a standard of care, as few doctors are skilled in this procedure. Even the most experienced surgeon cannot promise that a trachelectomy can be performed until after surgical microscopic examination, as the extent of the spread of cancer is unknown. If the surgeon is not able to microscopically confirm clear margins of cervical tissue once the patient is under general anesthesia in the operating room, a hysterectomy may still be needed. This can only be done during the same operation if the patient has given prior consent. Due to the possible risk of cancer spread to the lymph nodes in stage 1b cancers and some stage 1a cancers, the surgeon may also need to remove some lymph nodes from around the uterus for pathologic evaluation.

A radical trachelectomy can be performed abdominally or vaginally and there are conflicting opinions as to which is better. A radical abdominal trachelectomy with lymphadenectomy usually only requires a two to three day hospital stay, and most women recover very quickly (approximately six weeks). Complications are uncommon, although women who are able to conceive after surgery are susceptible to preterm labor and possible late miscarriage. It is generally recommended to wait at least one year before attempting to become pregnant after surgery. Recurrence in the residual cervix is very rare if the cancer has been cleared with the trachelectomy. Yet, it is recommended for patients to practice vigilant prevention and follow up care including pap screenings/colposcopy, with biopsies of the remaining lower uterine segment as needed (every 3–4 months for at least 5 years) to monitor for any recurrence in addition to minimizing any new exposures to HPV through safe sex practices until one is actively trying to conceive.

Early stages (IB1 and IIA less than 4 cm) can be treated with radical hysterectomy with removal of the lymph nodes or radiation therapy. Radiation therapy is given as external beam radiotherapy to the pelvis and brachytherapy (internal radiation). Patients treated with surgery who have high risk features found on pathologic examination are given radiation therapy with or without chemotherapy in order to reduce the risk of relapse.

Larger early stage tumors (IB2 and IIA more than 4 cm) may be treated with radiation therapy and cisplatin-based chemotherapy, hysterectomy (which then usually requires adjuvant radiation therapy), or cisplatin chemotherapy followed by hysterectomy.

Advanced stage tumors (IIB-IVA) are treated with radiation therapy and cisplatin-based chemotherapy.

On June 15, 2006, the US Food and Drug Administration approved the use of a combination of two chemotherapy drugs, hycamtin and cisplatin for women with late-stage (IVB) cervical cancer treatment. Combination treatment has significant risk of neutropenia, anemia, and thrombocytopenia side effects. Hycamtin is manufactured by GlaxoSmithKline.

Prognosis
Prognosis depends on the stage of the cancer. With treatment, the 5-year relative survival rate for the earliest stage of invasive cervical cancer is 92%, and the overall (all stages combined) 5-year survival rate is about 72%. These statistics may be improved when applied to women newly diagnosed, bearing in mind that these outcomes may be partly based on the state of treatment five years ago when the women studied were first diagnosed.

With treatment, 80 to 90% of women with stage I cancer and 50 to 65% of those with stage II cancer are alive 5 years after diagnosis. Only 25 to 35% of women with stage III cancer and 15% or fewer of those with stage IV cancer are alive after 5 years.

According to the International Federation of Gynecology and Obstetrics, survival improves when radiotherapy is combined with cisplatin-based chemotherapy.

As the cancer metastasizes to other parts of the body, prognosis drops dramatically because treatment of local lesions is generally more effective than whole body treatments such as chemotherapy.

Interval evaluation of the patient after therapy is imperative. Recurrent cervical cancer detected at its earliest stages might be successfully treated with surgery, radiation, chemotherapy, or a combination of the three. Thirty-five percent of patients with invasive cervical cancer have persistent or recurrent disease after treatment.

Average years of potential life lost from cervical cancer are 25.3 (SEER Cancer Statistics Review 1975-2000, National Cancer Institute (NCI)). Approximately 4,600 women were projected to die in 2001 in the US of cervical cancer (DSTD), and the annual incidence was 13,000 in 2002 in the US, as calculated by SEER. Thus the ratio of deaths to incidence is approximately 35.4%.

Regular screening has meant that pre cancerous changes and early stage cervical cancers have been detected and treated early. Figures suggest that cervical screening is saving 5,000 lives each year in the UK by preventing cervical cancer. About 1,000 women per year die of cervical cancer in the UK.

Epidemiology
Worldwide, cervical cancer is twelfth most common and the fifth most deadly cancer in women. It affects about 16 per 100,000 women per year and kills about 9 per 100,000 per year. Approximately 80% of cervical cancers occur in developing countries Worldwide, in 2008, it was estimated that there were 473,000 cases of cervical cancer, and 253,500 deaths per year.

In the United States, it is only the 8th most common cancer of women. In 1998, about 12,800 women were diagnosed in the US and about 4,800 died. In 2008 in the US an estimated 11,000 new cases were expected to be diagnosed, and about 3,870 were expected to die of cervical cancer. Among gynecological cancers it ranks behind endometrial cancer and ovarian cancer. The incidence and mortality in the US are about half those for the rest of the world, which is due in part to the success of screening with the Pap smear. The incidence of new cases of cervical cancer in the United States was 7 per 100,000 women in 2004. Cervical cancer deaths decreased by approximately 74% in the last 50 years, largely due to widespread Pap smear screening. The annual direct medical cost of cervical cancer prevention and treatment is prior to introduction of the HPV vaccine was estimated at $6 billion.

In the European Union, there were about 34,000 new cases per year and over 16,000 deaths due to cervical cancer in 2004.

In the United Kingdom, the age-standardised (European) incidence is 8.5/100,000 per year (2006). It is the twelfth most common cancer in women, accounting for 2% of all female cancers, and is the second most common cancer in the under 35s females, after breast cancer. The UK's European age-standardised mortality is 2.4/100,000 per year (2007) (Cancer Research UK Cervical cancer statistics for the UK). With a 42% reduction from 1988-1997 the NHS implemented screening programme has been highly successful, screening the highest risk age group (25–49 years) every 3 years, and those ages 50–64 every 5 years.

In Canada, an estimated 1,300 women will be diagnosed with cervical cancer in 2008 and 380 will die.

In Australia, there were 734 cases of cervical cancer (2005). The number of women diagnosed with cervical cancer has dropped on average by 4.5% each year since organised screening began in 1991 (1991–2005). Regular two-yearly Pap tests can reduce the incidence of cervical cancer by up to 90% in Australia, and save 1,200 Australian women dying from the disease each year.

History

 * 400 BCE - Hippocrates: cervical cancer incurable
 * 1925 - Hinselmann: invented colposcope
 * 1928 - Papanicolaou: developed Papanicolaou technique
 * 1941 - Papanicolaou and Trout: Pap smear screening
 * 1946 - Ayer: Aylesbury spatula to scrape the cervix, collecting sample for Pap smear
 * 1976 - Zur Hausen and Gisam: found HPV DNA in cervical cancer and warts
 * 1988 - Bethesda System for reporting Pap results developed
 * 2006 - First HPV vaccine FDA approved

Epidemiologists working in the early 20th century noted that cervical cancer behaved like a sexually transmitted disease. In summary:
 * 1) Cervical cancer was common in female sex workers.
 * 2) It was rare in nuns, except for those who had been sexually active before entering the convent. (Rigoni in 1841)
 * 3) It was more common in the second wives of men whose first wives had died from cervical cancer.
 * 4) It was rare in Jewish women.
 * 5) In 1935, Syverton and Berry discovered a relationship between RPV (Rabbit Papillomavirus) and skin cancer in rabbits. (HPV is species-specific and therefore cannot be transmitted to rabbits)

This led to the suspicion that cervical cancer could be caused by a sexually transmitted agent. Initial research in the 1940s and 1950s put the blame on smegma (e.g. Heins et al. 1958). During the 1960s and 1970s it was suspected that infection with herpes simplex virus was the cause of the disease. In summary, HSV was seen as a likely cause because it is known to survive in the female reproductive tract, to be transmitted sexually in a way compatible with known risk factors, such as promiscuity and low socioeconomic status. Herpes viruses were also implicated in other malignant diseases, including Burkitt's lymphoma, Nasopharyngeal carcinoma, Marek's disease and the Lucké renal adenocarcinoma. HSV was recovered from cervical tumour cells.

A description of human papillomavirus (HPV) by electron microscopy was given in 1949, and HPV-DNA was identified in 1963. It was not until the 1980s that HPV was identified in cervical cancer tissue. It has since been demonstrated that HPV is implicated in virtually all cervical cancers. Specific viral subtypes implicated are HPV 16, 18, 31, 45 and others.

In work that was initiated in the mid 1980s, the HPV vaccine was developed, in parallel, by researchers at Georgetown University Medical Center, the University of Rochester, the University of Queensland in Australia, and the U.S. National Cancer Institute. In 2006, the U.S. Food and Drug Administration (FDA) approved the first preventive HPV vaccine, marketed by Merck & Co. under the trade name Gardasil.

Society and culture
According to a survey, only 40% of American women had heard of human papillomavirus (HPV) infection and only 20% had heard of its link to cervical cancer.