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Causes
In recent years, scientists have made much progress toward understanding what happens in cells of the cervix when cancer develops. In addition, they have identified several risk factors that increase the odds that a woman might develop cervical cancer.
The development of normal human cells mostly depends on the information contained in the cells’ chromosomes. Chromosomes are large molecules of DNA. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than our outward appearance.
Some genes (packets of our DNA) have instructions for controlling when our cells grow and divide. Certain genes that promote cell division are called oncogenes. Others that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Cancers can be caused by DNA mutations (gene defects) that turn on oncogenes or turn off tumor suppressor genes. Scientists now think that HPV causes the production of 2 proteins known as E6 and E7. When these proteins are produced, they turn off some tumor suppressor genes. This may allow the cervical lining cells to grow uncontrollably, which in some cases will lead to cancer.
But HPV does not completely explain what causes cervical cancer. Most women with HPV don’t get cervical cancer, and certain other risk factors, like smoking and HIV infection, influence which women exposed to HPV are more likely to develop cervical cancer
Prevention
Since the most common form of cervical cancer starts with pre-cancerous changes, there are 2 ways to stop this disease from developing. The first way is to prevent the pre-cancers, and the second is to find and treat pre-cancers before they become cancerous.
Things to do to prevent pre-cancers
Avoid being exposed to HPV:You can prevent most pre-cancers of the cervix by avoiding exposure to HPV. Certain types of sexual behavior increase a woman's risk of getting HPV infection, such as:
having sex at an early age
having many sexual partners
having a partner who has had many sex partners
having sex with uncircumcised males
Delay sex: Waiting to have sex until you are older can help you avoid HPV. It also helps to limit your number of sexual partners and to avoid having sex with someone who has had many other sexual partners. Remember that someone can have HPV for years yet have no symptoms - it does not always cause warts or any other symptoms. Someone can have the virus and pass it on without knowing it.
Use condoms: Condoms provide some protection against HPV. One study found that when condoms are used correctly they can lower the HPV infection rate by about 70% - if they are used every time sex occurs. Condoms cannot protect completely because they don't cover every possible HPV-infected area of the body, such as skin of the genital or anal area. Still, condoms provide some protection against HPV, and they also protect against HIV and some other sexually transmitted diseases.
Don’t smoke: Not smoking is another important way to reduce the risk of cervical precancer and cancer.
Get vaccinated: Vaccines have been developed that can protect women from HPV infections. So far, a vaccine that protects against HPV types 6, 11, 16 and 18 (Gardasil®) and one that protects against types 16 and 18 (Cervarix®) have been studied.
Gardasil® has been approved for use in this country by the FDA. It requires a series of 3 injections over a 6-month period. The second injection is given 2 months after the first one, and the third is given 4 months after the second. Side effects are said to be mild. The most common one is short-term redness, swelling, and soreness at the injection site. In clinical trials, Gardasil prevented genital warts caused by HPV types 6 and 11 and prevented pre-cancers and cancers of the cervix caused by HPV types 16 and 18. This vaccine only works to prevent HPV infection -- it will not treat an infection that is already there.
To be most effective, the HPV vaccine should be given before a person starts having sex. The Federal Advisory Committee on Immunization Practices (ACIP) has recommended that the vaccine be given routinely to females aged 11 to 12. It can be given to younger females (as young as age 9) at the discretion of doctors. ACIP also recommended women ages 13 to 26 who have not yet been vaccinated get "catch-up" vaccinations.
The American Cancer Society also recommends that the vaccine be routinely given to females aged 11 to 12 and as early as age 9 years at the discretion of doctors. The Society also agrees that “catch-up” vaccinations should be given to females aged 13 to 18. The independent panel making the Society recommendations found that there was not enough proof of benefit to recommend catch-up vaccination for every woman aged 19 to 26 years. As a result, the American Cancer Society recommends that women aged 19 to 26 talk with their health care provider about the risk of previous HPV exposure and potential benefit from vaccination before deciding to get vaccinated. Research is now being done on using Gardasil in older women and in males. The American Cancer Society guideline focuses on Gardasil at this time. As new information on Cervarix®, Gardasil®, and other new products becomes available, these guidelines will be updated.
Gardasil is expensive - the vaccine series costs around $360 (not including any doctor’s fee or the cost of giving the injections). It should be covered by most medical insurance plans (if given according to ACIP guidelines). It should also be covered by government programs that pay for vaccinations in children under 18. Because this vaccine costs so much, you may want to check your coverage with your insurance company first.
It is important to realize that the vaccine doesn’t protect against all cancer-causing types of HPV, so routine Pap tests are still necessary. One other benefit of the vaccine is that it protects against the 2 viruses that cause 90% of genital warts.
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A risk factor is anything that changes your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for many cancers. But having a risk factor, or even several, does not mean that you will get the disease.
Several risk factors increase your chance of developing cervical cancer. Women without any of these risk factors rarely develop cervical cancer. Although these risk factors increase the odds of developing cervical cancer, many women with these risks do not develop this disease. When a woman develops cervical cancer or pre-cancerous changes, it may not be possible to say with certainty that a particular risk factor was the cause.
In thinking about risk factors, it helps to focus on those that you can change or avoid (like smoking or human papilloma virus infection), rather than those that you cannot (such as your age and family history). However, it is still important to know about risk factors that cannot be changed, because it's even more important for women who have these factors to get regular Pap tests to detect cervical cancer early.
Cervical cancer risk factors include:
Human papilloma virus infection: The most important risk factor for cervical cancer is infection by the human papilloma virus (HPV). HPV is a group of more than 100 related viruses. They are called papilloma viruses because some of them cause a type of growth called a papilloma. Papillomas are not cancers, and are more commonly called warts. HPV is passed from one person to another during skin-to-skin contact. HPV can be spread during sex - including vaginal intercourse, anal intercourse, and even during oral sex.
Doctors believe that women must have been infected by HPV before they develop cervical cancer. Certain types of HPV are called "high-risk" types because they are often the cause of cancer of the cervix. These types include HPV 16, HPV 18, HPV 31, HPV 33, and HPV 45, as well as some others. About two-thirds of all cervical cancers are caused by HPV 16 and 18.
Different types of HPVs cause warts on different parts of the body. Some types cause common warts on the hands and feet. Other types tend to cause warts on the lips or tongue.
Still other types of HPV may cause warts on or around the female and male genital organs and in the anal area. These warts may barely be visible or they may be several inches across. The medical term for genital warts is condyloma acuminatum. Two types of HPV, HPV 6 and HPV 11, cause most cases of genital warts. These two types are seldom linked to cervical cancer, and so are called "low-risk" types of HPV. Other sexually transmitted HPVs have been linked with genital or anal cancers in both men and women.
Many women become infected with HPV, but very few will ever develop cervical cancer. In most cases the body's immune system fights off the virus, and the infection goes away without any treatment. For reasons that we don't understand, the infection persists in some women and can cause cervical cancer. Although there is currently no cure for HPV infection, there are ways to treat the warts and abnormal cell growth that HPV causes.
The Pap test looks for changes in cervical cells caused by HPV infection. Newer tests look for HPV infections by finding genes (DNA) from HPV in the cells. Some doctors use the test for HPV to help decide what to do when a woman has a mildly abnormal Pap test result. If the test finds a high-risk type of HPV, it may mean she will need a full evaluation with a colposcopy procedure.
HPV infections occur mainly in young women and are less common in women over 30. The reason for this is not clear. Uncircumcised men are thought to be more likely to have the virus and be able to pass it on to someone else. HPV infection can be present for years without any symptoms. Even when someone doesn't have visible warts (or any other symptom), he (or she) can still be infected with HPV and pass the virus to somebody else.
Condoms ("rubbers") do provide some protection against HPV, but they cannot completely protect against infection. This is because HPV can still be passed from one person to another by skin-to-skin contact with an HPV-infected area of the body that is not covered by a condom - like the skin in the genital or anal area. Still, it is important to use condoms to protect against AIDS and other sexually transmitted illnesses that are passed on through some body fluids.
Vaccines have been developed to help prevent infection with some types of HPV. Right now, there is an HPV vaccine that has been approved for use in the United States by the Food and Drug Administration (FDA). This vaccine is called Gardasil®, and it protects against HPV types 6, 11, 16, and 18. More HPV vaccines are being developed and tested.
Although it is necessary to have had HPV for cervical cancer to develop, most women with this virus do not develop cancer. Doctors believe that other factors must come into play for cancer to develop. Some of the known factors are listed below.
Smoking: Women who smoke are about twice as likely as non-smokers to get cervical cancer. Smoking exposes the body to many cancer-causing chemicals that affect more than the lungs. These harmful substances are absorbed by the lungs and carried in the bloodstream throughout the body. Tobacco by-products have been found in the cervical mucus of women who smoke. Researchers believe that these substances damage the DNA of cervix cells and may contribute to the development of cervical cancer.
Immunosuppression: Human immunodeficiency virus (HIV), the virus that causes AIDS, damages the body's immune system and seems to make women more at risk for HPV infections. This may be what increases the risk of cervical cancer in women with AIDS. Scientists believe that the immune system is important in destroying cancer cells and slowing their growth and spread. In women with HIV, a cervical precancer might develop into an invasive cancer faster than it normally would.
Chlamydia infection: Chlamydia is a relatively common kind of bacteria that can infect the reproductive system. It is spread by sexual contact. Some studies have seen a higher risk of cervical cancer in women whose blood test results show past or current chlamydia infection (compared with women with normal test results). Infection with chlamydia often causes no symptoms in women. A woman may not know that she is infected at all unless she is tested for chlamydia when she gets her pelvic exam. Long-term chlamydia infection can cause pelvic inflammation, leading to infertility.
Diet: Women with diets low in fruits and vegetables may be at increased risk for cervical cancer. Also overweight women are more likely to develop this cancer.
Oral contraceptives (birth control pills): There is evidence that taking oral contraceptives (OCs) for a long time increases the risk of cancer of the cervix. Research suggests that the risk of cervical cancer goes up the longer a woman takes OCs, but the risk goes back down again after the OCs are stopped. In a recent study, the risk of cervical cancer was doubled in women who took birth control pills longer than 5 years, but the risk returned to normal 10 years after they were stopped.
The American Cancer Society believes that a woman and her doctor should discuss whether the benefits of using OCs outweigh the potential risks. A woman with multiple sexual partners should use condoms to lower her risk of sexually transmitted illnesses no matter what other form of contraception she uses.
Multiple pregnancies: Women who have had many full-term pregnancies have an increased risk of developing cervical cancer. No one really knows why this is true. One theory is this may be because some of the women may have been exposed more to HPV through un-protected sexual contact. Also, studies have pointed to hormonal changes during pregnancy as possibly making women more susceptible to HPV infection or cancer growth. Another thought is that the immune system of pregnant women might be weaker, allowing for HPV infection and cancer growth.
Low socioeconomic status: Poverty is also a risk factor for cervical cancer. Many women with low incomes do not have ready access to adequate health care services, including Pap tests. This means they may not get screened or treated for pre-cancerous cervical disease.
Diethylstilbestrol (DES): DES is a hormonal drug that was given to some women to prevent miscarriage between 1940 and 1971. Women whose mothers took DES (when pregnant with them) develop clear-cell adenocarcinoma of the vagina or cervix more often than would normally be expected. There is about 1 case of this type of cancer in every 1,000 women whose mothers took DES during pregnancy. This means that about 99.9% of "DES daughters" do not develop these cancers.
DES-related clear cell adenocarcinoma is more common in the vagina than the cervix. The risk appears to be greatest in women whose mothers took the drug during their first 16 weeks of pregnancy. The average age of women when they are diagnosed with DES-related clear-cell adenocarcinoma is 19 years. Since the use of DES during pregnancy was stopped by the FDA in 1971, even the youngest DES daughters are older than 35 - past the age of highest risk. Still, there is no age cut-off when these women are safe from DES-related cancer - doctors do not know exactly how long women will remain at risk.
DES daughters may also be at increased risk of developing pre-cancerous changes of cervical squamous cells and squamous cell cancer of the cervix. These pre-cancers and cancers seem to be linked to HPV.
Although DES daughters have an increased risk of developing clear cell carcinomas, women don’t have to be exposed to DES for clear cell carcinoma to develop. In fact, women were diagnosed with the disease before DES was developed.
Family history of cervical cancer: Cervical cancer may run in some families. If your mother or sister had cervical cancer, your chances of developing the disease are increased by 2 to 3 times. Some researchers suspect that some instances of this familial tendency are caused by an inherited condition that makes some women less able to fight off HPV infection than others. In other instances, women from the same family as a patient already diagnosed may be more likely to have one or more of the other non-genetic risk factors previously described in this section
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Introduction
The cervix is the lower part of the uterus (womb). It is sometimes called the uterine cervix. The body (upper part) of the uterus, is where a fetus grows. The cervix connects the body of the uterus to the vagina (birth canal). The part of the cervix closest to the body of the uterus is called the endocervix. The part next to the vagina is the exocervix (or ectocervix). The place where these 2 parts meet is called the transformation zone. Most cervical cancers start in the transformation zone.
Cervical cancers and cervical pre-cancers are classified by how they look under a microscope. There are 2 main types of cervical cancers: squamous cell carcinoma and adenocarcinoma. About 80% to 90% of cervical cancers are squamous cell carcinomas. These cancers are from the squamous cells that cover the surface of the exocervix. Under the microscope, this type of cancer is made up of cells that are like squamous cells. Squamous cell carcinomas most often begin where the exocervix joins the endocervix.
The remaining 10% to 20% of cervical cancers are adenocarcinomas. Adenocarcinomas are becoming more common in women born in the last 20 to 30 years. Cervical adenocarcinoma develops from the mucus-producing gland cells of the endocervix. Less commonly, cervical cancers have features of both squamous cell carcinomas and adenocarcinomas. These are called adenosquamous carcinomas or mixed carcinomas.
Although cervical cancers start from cells with pre-cancerous changes (pre-cancers), only some of the women with precancers of the cervix will develop cancer. The change from precancer to cancer usually takes several years - but it can happen in less than a year. For most women, pre-cancerous cells will go away without any treatment. Still, in some women pre-cancers turn into true (invasive) cancers. Treating all pre-cancers can prevent almost all true cancers.
Pre-cancerous changes are separated into different categories based on how the cells of the cervix look under a microscope.
Although almost all cervical cancers are either squamous cell carcinomas or adenocarcinomas, other types of cancer also can start in the cervix. These other types, such as melanoma, sarcoma, and lymphoma, occur more commonly in other parts of the body. This document discusses the more common cervical cancer types, and will not further discuss these rare types
Causes 
