Abnormal Pap Smear and Colposcopy

In Singapore there are over 200 patients with cancer of the neck of the womb (cervix) discovered every year, many of them at an advanced stage. The disease is preventable as its early stage can usually be detected by the screening test called Pap smear.

Pap smear is done by scraping the cells from the cervix using a brush and smears them on a glass slide. The cells are then processed in the laboratory and examined under microscope. Sometimes the cells may appear abnormal due to infection or inflammation and they are not cancerous. It is important to remember that abnormal conditions do not always become cancerous.

The following terms have been used to describe abnormal results:

• Dysplasia. This is not cancer, although it may develop into very early cancer of the cervix. The cells look abnormal under the microscope, but they do not invade nearby healthy tissue. There are various degrees of dyplasia.
  
• Squamous intraepithelial lesion (SIL). The squamous cells describes the thin, flat cells that form the outer surface of the cervix. An intraepithelial lesion means that the abnormal cells are present only in the layer of cells on the surface of the cervix. It may be low-grade or high- grade.
  
• Cervical intraepithelial neoplasia (CIN). Neoplasia means an abnormal growth of cells. There are 3 types of CIN (number 1 to 3), depending on how much of the thickness of the lining of the cervix contains abnormal cells. CIN 3 is another term for carcinoma in situ ,a condition where cancer is present only in the layer of cells on the surface of the cervix, and has not spread to nearby tissues.
  
• Atypical squamous cells. These are abnormal cells where there is no definite disease but further test or follow¨Cup is necessary.
  
• Cervical cancer, or invasive cervical cancer, occurs when abnormal cells spread deeper into the cervix or to the surrounding tissues or organs.

Pap smear is therefore not a perfect test. It may either miss the cancer lesion on the cervix (false negative result) or it may falsely report an abnormality when there is none (false positive result). Therefore, it cannot be used to make a diagnosis.

The vast majority of women with abnormal Pap smears do not have cancer. They need further examination by colposcopy. If there is any abnormality, it can be dealt with rapidly so as to prevent cancer from occurring.

Colposcope is a microscope with a powerful light source. The cervix is examined under magnification after applying a variety of liquids. The examination is relatively painless and it takes about 10-15 minutes to complete. During the examination, if an abnormality is detected, a small piece of tissue from the cervix is taken (biopsy) for further examination in the laboratory (histology).