The Pap test, also called a Pap smear, checks for changes in the cells of your cervix. The Pap test can tell if you have an infection, abnormal (unhealthy) cervical cells, or cervical cancer.
It can find the earliest signs of cervical cancer – a common cancer in women. If caught early, the chance of curing cervical cancer is very high. Pap tests also can find infections and abnormal cervical cells that can turn into cancer cells. Treatment can prevent most cases of cervical cancer from developing.

The Pap smear is a simple procedure. Cells are collected from the cervix and placed (smeared) onto a slide. The slide is sent to a laboratory where the cells are tested for anything unusual. If abnormal changes are found at screening, further tests will be done to see if treatment is needed.
A Pap smear only takes a few minutes. No drugs or anesthetics are required.

There are many reasons for “abnormal” Pap test results. If results of the Pap test are unclear or show a small change in the cells of the cervix, your doctor will probably repeat the Pap test.

While an abnormal Pap smear may be a sign of cancer, many different changes on your cervix can cause an abnormal Pap smear. Pap smears can be abnormal if the cervix is inflamed or irritated. This can be caused by an infection of the cervix, douching, menopausal changes, or irritation. The cervix may also be going through some changes called dysplasia. Dysplasia means the cells on the Pap smear look abnormal under the microscope. Dysplasia isn’t the same thing as cancer but may lead to cancer if it is not treated.

If the test finds more serious changes in the cells of the cervix, the doctor will suggest more powerful tests. Results of these tests will help your doctor decide on the best treatment. These include:

• Colposcopy: The doctor uses a tool called a colposcope to see the cells of the vagina and cervix in detail.
• Endocervical curettage: The doctor takes a sample of cells from the endocervical canal with a small spoon-shaped tool called a curette.
• Biopsy: The doctor removes a small sample of cervical tissue. The sample is sent to a lab to be studied under a microscope.

The Bethesda System is a method of classifying Pap smear results. It uses the term squamous intraepithelial lesion (SIL) to describe abnormal changes in the cells on the surface of the cervix. Squamous refers to thin, flat cells that lie on the outer surface of the cervix. An intraepithelial lesion occurs when normal cells on the cervical surface are replaced by a layer of abnormal cells, and these changes are classified as high grade or low grade.

• ASCUS (atypical squamous cells of undetermined significance) – Borderline, some abnormal cells
• LGSIL (low-grade squamous intraepithelial lesions) – Mild dysplasia and cellular changes associated with HPV
• HGSIL (high-grade squamous intraepithelial lesions) – Moderate to severe dysplasia, precancerous lesions, and carcinoma in-situ (preinvasive cancer that involves only the surface cells)

Cervical intraepithelial neoplasia (CIN) refers to new abnormal cell growth. Intraepithelial refers to the surface layers of the cells. The CIN System grades the degree of cell abnormality numerically, CIN I is the lowest and CIN III is the highest.

CIN Grading System

• Atypia – correlates with ASCUS
• CIN I – mild dysplasia and correlates with LGSIL
• CIN II – moderate dysplasia and correlates with HGSIL
• CIN III – severe dysplasia and correlates with HGSIL
• Carcinoma in-situ
• Cervical cancer

Comparison of PAP smear classification systems
The following table is an estimated equivalent terms in the various systems of PAP smear classification.

Notes:

• CIS – Carcinoma in situ
• WNL – Within Normal Limits
• BCC – Benign cellular changes. These include those due to infection, atrophy, radiation or repair.
• ASCUS – Atypical squamous cells of undetermined significance. A high percentage of these cases will be found to have more severe lesion (LGSIL or HGSIL) subsequently.
• AGUS – Atypical glandular cells of undetermined significance.
• LGSIL – Low grade squamous intraepithelial lesion. This is includes CIN I changes. Cellular changes due to HPV are usually classified at least as LGSIL.
• HGSIL – High grade squamous intraepithelial lesion. This includes CIN II and III changes on histology.