Guest Author - Denise Howard, M.D., M.P.H.
The institution of routine Pap testing has dramatically decreased the incidence of cervical cancer. In the United States it is estimated to have decreased by 75% in the past 40 years. Cervical cancer develops over a period of 10 years or more. This long transition period makes it possible to detect the precancerous changes at a stage in which treatment is feasible. This is the goal of the Pap test.
The Pap is a screening test. The goal of a screening test is to identify all cases of cervical abnormalities. This however, results in many instances when the Pap is mistaken in its report of an abnormality. The next step in the screening process then becomes a more definitive diagnostic test, which is usually more invasive, but able to give a more accurate report.
The Pap test obtains cells from the cervix which is then examined for changes that reflect cervical dysplasia or cervical cancer. The reported abnormalities may include atypical squamous cells, low grade squamous intraepithelial lesion, high grade squamous intraepithelial lesion which includes moderate and severe dysplasia, atypical glandular cells, and carcinoma. Further evaluation is dependent on the report. The most common abnormalities reported are atypical squamous cells and dysplasia (also described as low or high grade squamous intraepithelial lesion).
The addition of Human Papilloma Virus (HPV) testing has made identification of true cervical abnormalities much easier. The known association of HPV virus types with dysplasia and cervical cancer allows for more aggressive management of those at greater risk. If the Pap test has atypical squamous cells and HPV testing reveals the presence of the high risk virus types then colposcopic evaluation is indicated. If the pap reflects any degree of dysplasia a colposcopy is also required.
Colposcopy is a procedure in which the cervix is examined under magnification after being painted with a weak acidic solution. The solution is taken up by abnormal cells and these cells are easily visualized with a magnified view. The identification of areas of abnormality then allows directed biopsy. A tiny sample of tissue is obtained and sent for pathologic examination. This gives the pathologist a sample of tissue rather than a few cells to evaluate allowing for a much easier diagnosis.
Once dysplasia is diagnosed then management can be determined. Low grade dysplasia typically resolves on its own, especially in younger women. Thus observation with serial Pap test every 3-4 months to document resolution would be one management option. The loop electrosurgical excision procedure (LEEP) is the most common method for managing dyplasia in the office setting. It is a simple, quick and effective procedure. Removing the involved area provides treatment for the dysplasia and prevents cervical cancer development. The excised tissue can also provide an even larger tissue sample to the pathologist who can then make an even more definitive diagnosis. Other possible treatments might include a cone biopsy which is typically performed in the operating room using a scalpel to obtain an even more precise sample. This is typically done when cancer is suspected and the presence of invasion needs to be documented.
It is unusual to diagnose cervical cancer. The early diagnosis and appropriate treatment of cervical dysplasia has been an effective strategy in cervical cancer prevention. When cervical cancer is diagnosed it is usually in some one who has not had a Pap test in many years. The identification of HPV virus as the causative agent of cervical cancer has allowed the development of a vaccination which has the potential to decrease the incidence of cervical cancer even further and decrease the incidence of dysplasia.
