What is cancer?
The body is made up of trillions of living cells. Normal body cells grow, divide, and die
in an orderly fashion. During the early years of a person’s life, normal cells divide faster
to allow the person to grow. After the person becomes an adult, most cells divide only to
replace worn-out or dying cells or to repair injuries.
Cancer begins when cells in a part of the body start to grow out of control. There are
many kinds of cancer, but they all start because of out-of-control growth of abnormal
Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells
continue to grow and form new, abnormal cells. Cancer cells can also invade (grow into)
other tissues, something that normal cells cannot do. Growing out of control and invading
other tissues are what makes a cell a cancer cell.
Cells become cancer cells because of damage to DNA. DNA is in every cell and directs
all its actions. In a normal cell, when DNA gets damaged the cell either repairs the
damage or the cell dies. In cancer cells, the damaged DNA is not repaired, but the cell
doesn’t die like it should. Instead, this cell goes on making new cells that the body does
not need. These new cells will all have the same damaged DNA as the first cell does.
People can inherit damaged DNA, but most DNA damage is caused by mistakes that
happen while the normal cell is reproducing or by something in our environment.
Sometimes the cause of the DNA damage is something obvious, like cigarette smoking.
But often no clear cause is found.
In most cases the cancer cells form a tumor. Some cancers, like leukemia, rarely form
tumors. Instead, these cancer cells involve the blood and blood-forming organs and
circulate through other tissues where they grow.
Cancer cells often travel to other parts of the body, where they begin to grow and form
new tumors that replace normal tissue. This process is called metastasis. It happens when
the cancer cells get into the bloodstream or lymph vessels of our body.
No matter where a cancer may spread, it is always named for the place where it started.
For example, breast cancer that has spread to the liver is still called breast cancer, not
liver cancer. Likewise, prostate cancer that has spread to the bone is metastatic prostate
cancer, not bone cancer.
Different types of cancer can behave very differently. For example, lung cancer and
breast cancer are very different diseases. They grow at different rates and respond to
different treatments. That is why people with cancer need treatment that is aimed at their
particular kind of cancer.
Not all tumors are cancerous. Tumors that aren’t cancer are called benign. Benign tumors
can cause problems – they can grow very large and press on healthy organs and tissues.
But they cannot grow into (invade) other tissues. Because they can’t invade, they also
can’t spread to other parts of the body (metastasize). These tumors are almost never life
What is cervical cancer?
The cervix is the lower part of the uterus (womb). It is sometimes called the uterine
cervix. The body of the uterus (the upper part) is where a baby 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 2 main types of cells covering the cervix are squamous
cells (on the exocervix) and glandular cells (on the endocervix). The place where these 2
cell types meet is called the transformation zone. Most cervical cancers start in the
Most cervical cancers begin in the cells lining the cervix. These cells do not suddenly
change into cancer. Instead, the normal cells of the cervix first gradually develop precancerous
changes that turn into cancer. Doctors use several terms to describe these precancerous
changes, including cervical intraepithelial neoplasia (CIN), squamous
intraepithelial lesion (SIL), and dysplasia. These changes can be detected by the Pap test
and treated to prevent the development of cancer (see “Can cervical cancer be
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.
Most of the other cervical cancers are adenocarcinomas. Cervical adenocarcinomas seem
to have becoming more common in the past 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 pre-cancers of the cervix will develop cancer. The change from
cervical pre-cancer to cervical 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 precancers
can prevent almost all true cancers. Pre-cancerous changes and specific types of
treatment for pre-cancers are discussed in the sections, “How are cervical cancers and
pre-cancers diagnosed?” and “Treating pre-cancers and other abnormal Pap test results.”
Pre-cancerous changes are separated into different categories based on how the cells of
the cervix look under a microscope. These categories are discussed in the section, “How
are cervical cancers and pre-cancers diagnosed?”
Although almost all cervical cancers are either squamous cell carcinomas or
adenocarcinomas, other types of cancer also can develop in the cervix. These other types,
such as melanoma, sarcoma, and lymphoma, occur more commonly in other parts of the
This document discusses the more common cervical cancer types, and will not
further discuss these rare types.
What are the key statistics about cervical cancer?
The American Cancer Society’s most recent estimates for cervical cancer in the United
States are for 2011:
· About 12,710 new cases of invasive cervical cancer will be diagnosed.
· About 4,290 women will die from cervical cancer.
Some researchers estimate that non-invasive cervical cancer (carcinoma in situ) occurs
about 4 times more often than invasive cervical cancer.
Cervical cancer was once one of the most common causes of cancer death for American
women. Then, between 1955 and 1992, the cervical cancer death rate declined by almost
70%. The main reason for this change was the increased use of the Pap test. This
screening procedure can find changes in the cervix before cancer develops. It can also
find cervical cancer early — in its most curable stage. The death rate from cervical cancer
continues to decline by nearly 3% each year.
Cervical cancer tends to occur in midlife. Most cases are found in women younger than
50. It rarely develops in women younger than 20. Many older women do not realize that
the risk of developing cervical cancer is still present as they age. Almost 20% of women
with cervical cancer are diagnosed when they are over 65. That is why it is important for
older women to continue having regular Pap tests. See the section, “Can cervical cancer
be prevented?” for more specific information on current American Cancer Society
In the United States, cervical cancer occurs most often in Hispanic women; at a rate that
is more than twice that seen in non-Hispanic white women. African-American women
develop this cancer about 50% more often than non-Hispanic white women.
What are the risk factors for cervical cancer?
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 you can change or avoid (like
smoking or human papilloma virus infection), rather than those 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 that can infect cells on the
surface of the skin, genitals, anus, mouth and throat, but not the blood or most internal
organs such as the heart or lungs. These viruses are called papilloma viruses because
some of them cause a type of growth called a papilloma, which are more commonly
known as warts..
Different types of HPVs cause warts on different parts of the body. Some cause common
warts on the hands and feet; others 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.
These are known as genital warts or condyloma acuminatum. HPV 6 and HPV 11 are the
2 types of HPV that cause most cases of genital warts. They are called low-risk types of
HPV because they are seldom linked to cancer.
Certain types of HPV are called high-risk types because they are strongly linked to
cancers, including cancer of the cervix, vulva, and vagina in women, penile cancer in
men, and anal and oral cancer in both men and women. In fact, doctors believe that a
woman must be infected by HPV before she develops cervical cancer. The high-risk
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.
Infection with HPV is common, and in most people the body is able to clear the infection
on its own. Sometimes, however, the infection does not go away and becomes chronic.
Chronic infection, especially when it is caused by certain high-risk HPV types, can
eventually cause certain cancers, such as cervical cancer.
Although HPV can be spread during sex — including vaginal intercourse, anal
intercourse, and oral sex – sex doesn’t have to occur for the infection to spread. All that is
needed to pass HPV from one person to another is skin-to-skin contact with an area of the
body infected with HPV. Infection with HPV seems to be able to be spread from one part
of the body to another — for example, infection may start in the cervix and then spread to
the vagina. The only sure way to completely prevent anal and genital HPV infection is to
never allow another person to have contact with those areas of the body.
The Pap test looks for changes in cervical cells caused by HPV infection. Newer tests
look for the infections themselves 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 can mean she will
need a full evaluation with a colposcopy procedure. Although there is currently no cure
for HPV infection, there are ways to treat the warts and abnormal cell growth that HPV
For more information on preventing HPV infection, see the section “Things to do to
prevent cervical pre-cancers” in this document or ask for our document Human
Papilloma Virus (HPV), Cancer, and HPV Vaccines: Frequently Asked Questions.
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 organs other
than the lungs. These harmful substances are absorbed through 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.
Smoking also makes the immune system less effective in fighting HPV infections.
Human immunodeficiency virus (HIV), the virus that causes AIDS, damages the body’s
immune system and places women at higher risk for HPV infections. This may explain
the increased risk of cervical cancer for 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 pre-cancer might develop into an invasive cancer
faster than it normally would. Another group of women at risk of cervical cancer are
women receiving drugs to suppress their immune response, such as those being treated
for an autoimmune disease (in which the immune system sees the body’s own tissues as
foreign and attacks them, as it would a germ) or those who have had an organ transplant.
Chlamydia is a relatively common kind of bacteria that can infect the reproductive
system. It is spread by sexual contact. Chlamydia infection can cause pelvic
inflammation, leading to infertility. Some studies have seen a higher risk of cervical
cancer in women whose blood test results show evidence of past or current chlamydia
infection (compared with women who have 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.
Women with diets low in fruits and vegetables may be at increased risk for cervical
cancer. Also overweight women are more likely to develop adenocarcinoma of the
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
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 full-term pregnancies
Women who have had 3 or more full-term pregnancies have an increased risk of
developing cervical cancer. No one really knows why this is true. One theory is that these
women had to have had unprotected intercourse to get pregnant, so they may have had
more exposure to HPV. 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.
Young age at the first full-term pregnancy
Women who were younger than 17 years when they had their first full-term pregnancy
are almost 2 times more likely to get cervical cancer later in life than women who waited
to get pregnant until they were 25 years or older.
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 cervical pre-cancers.
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. This type of cancer is extremely rare in non-DES exposed women. 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
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 DESrelated
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 squamous cell cancers and
pre-cancers of the cervix linked to HPV.
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 2 to 3 times higher than if no one in the family
had it. 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.