Lab Tests for Cervical Cancer Detection

When cells grow in an uncontrolled and potentially harmful manner in the cervix, cervical cancer is the result. The cervix is the cone-shaped passage that connects the vagina to the lower portion of the uterus. 

A persistent viral infection causes most cases of cervical cancer. The viruses responsible are strains of human papillomavirus or HPV. HPV is transmitted sexually and is extremely common. 

High-Risk HPV: 14 of the different identified strains of HPV are likely to cause cancer. Two of these type 16 and type 18, are responsible for approximately 80 percent of all cervical cancer cases. 

Low-Risk HPV: There are a few strains of HPV that rarely cause cancer, instead usually causing genital warts. HPV-6 and HPV-11 produce ninety percent of all genital warts, but these strains are considered “low-risk” for cervical cancer. 

The human body is often able to clear an HPV infection without medical treatment. When a high-risk HPV strain goes untreated and is not cleared by the body, it can eventually cause cervical cancer. The development process that leads from the infection to cancer takes many years. High-risk HPV strains cause the uncontrolled growth of infected cells in the cervix. The body’s immune system will usually recognize these cells as unwanted and limit their growth. If the cells remain and develop, they can become precancerous. 

Precancerous cells may be found on the outside or the inside of the cervix. They are visually different from normal, healthy cells. Precancerous and cancerous cervix cells start on the linings of the cervix. If they are not treated, they can become invasive and start spreading into the deeper tissues of the cervix. From there, they may eventually spread throughout the body. 

Cervical cancer can be divided into two broad categories: 

Squamous cell carcinoma: These are cancers in the squamous (flat) cells that line the outside of the cervix. Squamous cell carcinoma accounts for the great majority of cervical cancer cases. Data collected by the American Cancer Society suggests that nine out of 10 cervical cancer cases are squamous cell carcinoma. 

Adenocarcinomas: Most remaining cases of cervical cancer are adenocarcinomas. In these cancers, the faulty cells start in the mucus-producing glands at the opening of the cervix, the endocervix. 

On very rare occasions, a case of cervical cancer may involve both types of cancer cells growing in the same patient. 

Cervical cancer can be successfully treated by surgically removing the cancerous cells. This is particularly effective when the cancer is detected early. Women who are treated for early-stage cervical cancer have a 5-year survival rate of more than 90 percent. 

If the cancer spreads beyond the cervix’s surface, effective treatment may require a hysterectomy, chemotherapy, and/or radiation treatment. The longer cervical cancer goes untreated, the greater its chance of spreading (metastasizing) to nearby tissues and organs. The uterus, bladder, rectum, and abdominal wall are all at risk. Cervical cancer can spread throughout the entire body if it first reaches the pelvic lymph nodes. Survival rates and rates of successful treatment decline as cases grow further beyond the initial organ. Widespread cervical cancer is usually fatal. 

According to the American Cancer Society, yearly diagnoses of cervical cancer in the US exceed 13,000 cases. Each year, 4,250 women are likely to die of the disease. In the past, invasive cervical cancer was a far more common and serious disease in the US.  

The Papanicolaou smear (commonly called the Pap smear or Pap test) has dramatically improved detection rates for cervical cancer. This screening test allows for the early and accurate detection of cancerous and precancerous cells in the cervix. Its adoption has reduced cervical cancer rates in industrialized nations (including the US) by up to 70 percent. The latest additions to the cervical cancer detection toolkit are accurate tests that can detect the presence of specific high-risk strains of HPV. 

While the detection and treatment of cervical cancer have improved considerably, the disease is still a serious threat, particularly in certain US populations at increased risk. Hispanic women, for example, have the highest cervical cancer rates. The disease is also more serious in developing nations, where women have limited access to tests and healthcare. The World Health Organization asserts that cervical cancer is the second-most common form of cancer among female populations in developing nations. The developing world sees more than half a million new cervical cancer diagnoses every year. Eighty-five percent of deaths related to cervical cancer occur in developing nations. 

Risk Factors:

As already noted, a persistent infection with a strain of human papillomavirus (HPV), particularly a high-risk one, is the key risk factor for cervical cancer. 

The National Cancer Institute does note that other factors can make cervical cancer development more likely after you have an HPV infection. The key secondary factors are long-term use of oral contraceptives (birth control pills), bringing three or more pregnancies to term, and smoking. 

These conditions can also increase the risk of cervical cancer: 

  • A weakened or compromised immune system (e.g., with an HIV infection or following an organ transplant) 
  • An unhealthy diet lacking fruits and vegetables 
  • Being overweight 
  • A history of cervical cancer in older relatives 
  • A history of chlamydia infection 
  • A history of DES exposure before birth (DES is a drug given to some pregnant women from 1940 to 1971 to prevent miscarriages) 

Signs and Symptoms  

Neither an HPV infection nor precancerous cell growth in the cervix normally causes any detectable symptoms. Testing is the only way to find out if either condition is present. 

General symptoms that may be caused by cervical cancer include abnormal bleeding between menstrual periods, bleeding after intercourse, or increased vaginal discharge. These symptoms usually only appear after cervical cancer has fully developed and become invasive; the cancer may already have spread to other tissues. 

Note that these symptoms can be caused by a wide range of conditions other than cervical cancer. Talk to a healthcare provider to find out what is causing any such symptoms. You should also establish a schedule for preventive cervical cancer screening if you do not have symptoms. 

Tests 

  • Pap Smear (AKA Pap Test) 

The Papanicolaou (Pap) smear is an effective, widely used test that screens for precancerous or cancerous changes in the cervix. Cells on the inside and outside lining of the cervix start to change appearance as soon as they become precancerous. When detected on a Pap smear, such different cells are called “atypical cells.” The presence of precancerous cells is not the only condition that can lead to atypical cells; they may also appear if the cervix lining is irritated or the patient has an infection. The appearance of atypical cells continues to change as they grow toward cancer. Intermediate cellular changes detected in a Pap smear are called low or high-grade squamous intraepithelial lesions. 

  • HPV Test 

The HPV test is a cervical cancer screening test that is primarily administered to women who are over the age of 30. HPV testing may be performed on younger women if they are at increased risk of developing cervical cancer. The test detects any infection with high-risk strains of human papillomavirus (hrHPV). If such an infection becomes persistent, it can start causing cervical cell changes that may lead to the development of cancer. With the link between hrHPV infection and cervical cancer now thoroughly established, HPV testing is a key part of women’s health screening. 

  • Recommendations 

A range of different professional organizations is in broad agreement on the best practices for cervical cancer screening. Recommendations are largely the same from the American Cancer Society, the American Society for Clinical Pathology (ASCP), the American College of Obstetricians and Gynecologists (ACOG), the US Preventive Services Task Force (USPSTF), the Society of Gynecologic Oncology and the American Society for Colposcopy and Cervical Pathology (ASCCP). 

Women between the ages of 30 and 65 are advised to discuss the benefits and drawbacks of the screening strategies described below with their healthcare providers. 

Preferred – Co-testing every five years with a Pap smear and a high-risk HPV (hrHPV) test 

Acceptable – Pap smears every three years 

Alternative – hrHPV tests every five years 

Pap smears are recommended at three-year intervals for women between the ages of 21 and 29. HPV testing is only recommended if a Pap test shows abnormal changes. 

Screening is not recommended for women under the age of 21 because cervical cancer is rare in this age group. False-positive results become too frequent in this age group, leading to unwanted stress and unnecessary treatment. 

Women over the age of 65 do not need screening if they have not experienced any abnormal cervical changes in the past.

One of the two following testing situations should also be true: 

  • Your last three Pap smears have been negative or 
  • You have had two negative co-tests (Pap smear + hrHPV) in the last ten years, with the most recent being no more than five years ago. 

It is important to continue regular screening for cervical cancer even if you receive the HPV vaccine. (See prevention.) 

Your healthcare provider should schedule screening more frequently if you have any increased risk factors for cervical cancer, including: 

  • DES (diethylstilbestrol) exposure when your mother was pregnant with you 
  • HIV infection 
  • Immune system compromise 
  • Previous diagnoses of cervical cancer or a high-grade precancerous lesion