by Chito Nwana MD on February 13, 2014
This article is taken from American Cancer Society (www.cancer.org)
Cervical Cancer: Prevention and Early Detection
What is cervical cancer?
Cervical cancer is cancer that starts in the cervix. 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 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 2 main types of cells covering the cervix are squamous cells (on the exocervix) and glandular cells (on the endocervix). The place these 2 cell types meet is called the transformation zone. Most cervical cancers start in the transformation zone.
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 gradually develop pre-cancerous changes that turn into cancer. Doctors use several terms to describe these pre-cancerous 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 cancer from developing (see the section Can cervical cancer be prevented).
Cervical cancers and cervical pre-cancers are classified by how they look under a microscope. There are 2 main types of cervical cancer: squamous cell carcinoma and adenocarcinoma. About 80% to 90% of cervical cancers are squamous cell carcinomas. These cancers start in 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.
Most of the remaining types of cervical cancers are adenocarcinomas. Cervical adenocarcinomas seem to have become more common 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 women with pre-cancers of the cervix will develop cancer. The change from pre-cancer to cancer usually takes several years but it can happen in less than a year. For most women, pre-cancerous cells will remain unchanged or even 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 and specific types of treatment for pre-cancers are discussed in the section, Can cervical cancer be prevented?
Importance of cervical cancer screening
The goal of screening for cervical cancer is to find cervix cell changes and early cervical cancers before they cause symptoms. Screening refers to the use of tests and exams to find a disease, such as cancer, in people who do not have any symptoms. Early detection means applying a strategy that results in an earlier diagnosis of cervical cancer than otherwise might have occurred. Screening tests offer the best chance to detect cervical cancer at an early stage when successful treatment is likely. Screening can also actually prevent most cervical cancers by finding abnormal cervix cell changes (pre-cancers) so that they can be treated before they have a chance to turn into a cervical cancer.
Cancer of the cervix may be prevented or detected early by regular screening with the Pap test (sometimes combined with a test for human papilloma virus). If its detected early, cervical cancer is one of the most successfully treatable cancers. In the United States, the cervical cancer death rate declined by almost 70% between 1955 and 1992, in large part due to the effectiveness of Pap test screening. In recent years, the death rates from cervical cancer have been stable.
Despite the recognized benefits of cervical cancer screening, not all American women take advantage of it. About half of the cervical cancers diagnosed in the United States are found in women who were never screened for the disease, with another 10% found in women who had not been screened within the past 5 years. In particular, older women, those without health insurance, and women who have recently immigrated are less likely to have regular cervical cancer screening.
Cervical cancer deaths are higher in populations around the world where women do not have routine cervical cancer screening. In fact, cervical cancer is the major cause of cancer deaths in women in many developing countries. These women are usually diagnosed with late stage cancers, rather than pre-cancers or early cancers.