Cervical Cancer Overview
What is cervical cancer?
Cervical cancer is cancer that starts in the cervix, the narrow opening into the uterus from the vagina. The normal "ectocervix" (the portion of the uterus extending into the vagina) is a healthy pink color and is covered with flat, thin cells called squamous cells. The "endocervix" or cervical canal is made up of another kind of cell called columnar cells. The area where these cells meet is called the "transformation zone" (T-zone) and is the most likely location for abnormal or precancerous cells to develop.
Most cervical cancers (80 to 90 percent) are squamous cell cancers. Adenocarcinoma is the second most common type of cervical cancer, accounting for the remaining 10 to 20 percent of cases. Adenocarcinoma develops from the glands that produce mucus in the endocervix. While less common than squamous cell carcinoma, the incidence of adenocarcinoma is on the rise, particularly in younger women.
More than 12,000 women in the United States will be diagnosed with cervical cancer each year, and more than 4,000 of women will die. Cervical cancer is the second most common type of cancer for women worldwide, but because it develops over time, it is also one of the most preventable types of cancer. Deaths from cervical cancer in the United States continue to decline by approximately 2 percent a year. This decline is primarily due to the widespread use of the Pap test to detect cervical abnormalities and allow for early treatment. Most women who have abnormal cervical cell changes that progress to cervical cancer have never had a Pap test or have not had one in the previous three to five years.
Cancer of the cervix tends to occur during midlife. Half of the women diagnosed with the disease are between 35 and 55 years of age. It rarely affects women under age 20, and approximately 20 percent of diagnoses are made in women older than 65. For this reason, it is important for women to continue cervical cancer screening until at least the age of 70. Some women need to continue screening longer, so ask your health care provider what’s best for you.
What causes cervical cancer?
Human papillomavirus (HPV) is found in about 99% of cervical cancers. There are over 100 different types of HPV, most of which are considered low-risk and do not cause cervical cancer. High-risk HPV types may cause cervical cell abnormalities or cancer. More than 70 percent of cervical cancer cases can be attributed to two types of the virus, HPV-16 and HPV-18, often referred to as high-risk HPV types.
HPV is estimated to be the most common sexually transmitted infection in the United States. In fact, by age 50 approximately 80% of women have been infected with some type of HPV. The majority of women infected with the HPV virus do NOT develop cervical cancer. For most women the HPV infection does not last long; 90% of HPV infections resolve on their own within 2 years. A small number of women do not clear the HPV virus and are considered to have “persistent infection. A woman with a persistent HPV infection is at greater risk of developing cervical cell abnormalities and cancer than a woman whose infection resolves on its own. Certain types of this virus are able to transform normal cervical cells into abnormal ones. In a small number of cases and usually over a long period of time (from several years to several decades), some of these abnormal cells may then develop into cervical cancer.