A PAP smear is a sampling of cervical cells done at the time of a pelvic exam. Although many people think of their annual preventative exam as their "PAP", the PAP is actually just one small aspect of this exam. The PAP screens only for precancers of the CERVIX, and sometimes the vagina, but not of the ovaries, the uterus, or the Fallopian tubes.

The test was discovered by a physician whose last name was "Papinicolou", hence the name. He found out that if you take a small scraping of cells from the outside of the cervix, smear them on a slide and look at them carefully under a microscope, precancerous changes can be detected. Specifically a larger size cell nucleus relative to cytoplasm indicated a higher risk.

At the time of his findings, cervical cancer was one of the leading causes of death from female cancers, and was especially common in young women. As a result of his discovery, the incidence of cervical cancer has decreased nearly 7 times!

Today the PAP is no longer a "smear", but instead is collected in a liquid and analyzed initially by a cytotechnologist. There are two parts to PAP smear collection. First the outside cells (known as "squamous cells") are collected by gently scraping the outside of the cervix with a plastic spatula. Next, the cells lining the cervical canal leading up to the cervix (known as "glandular cells") are sampled with an "endobrush". The cells are scraped off of these small disposable instruments into the liquid and sent to the lab.

There are strict criteria which must be met in order to classified as a normal PAP. These are internationally agreed upon standards called the "Bethesda system".

There are also strict criteria as to what constitutes an abnormal PAP. Thankfully we seldom see cancerous cells on PAPs anymore, and this is because doing regular PAPs allows us to catch cells while they are still in the long precancerous phase that leads to actual cancer.

WHAT CAUSES PRECANCEROUS CHANGES IN CERVICAL CELLS?

We now know a virus called HPV causes most of the precancerous changes in cervical cells. HPV is a sexually transmitted virus, carried by approximately 40% of the sexually active population. There are at least 70 different subtypes of HPV. Some of these cause genital warts, others do nothing, and still others, referred to as "high risk" subtypes, cause cervical precancer and ultimately cervical cancer in women. These high risk subtypes usually don't cause symptoms or problems for the males who carry them.

For women who carry this virus, their immune system does tend to suppress it to non-detectable levels over 18 to 24 months, but it can flare again when the immune system is suppressed, even many years later. During the time the infection is active, ahigh risk subtype of HPV can incorporate itself into the genetics of the cervical cells and cause the cell to divide in a way that the body is not in control of. When this happens the nuclei of the cell enlarges relative to the rest of the cell and this is the precancerous change we are looking for, and concerned about. This precancerous change is called DYSPLASIA.

WHAT ARE RISK FACTORS FOR HAVING HPV?

Risks factors for having HPV of any kind, including high risk subtypes are: (1) first sexual encounter at age <18; (2) multiple sexual partners, or a partner who has had multiple partners; (3) unprotected intercourse; (4) being on immune suppressant medications or having a medical condition which causes immune suppression; (4) history of chlamydia; gonorrhea or other STDs, since these are acquired in a similar manner.

WHAT ARE THE DIFFERENT KINDS OF ABNORMAL PAPS?

There are four basic kinds of abnormal PAPs:

1. LSIL (stands for "low grade squamous intra-epithelial lesion")

With this kind of PAP, the cells meet criteria for early dysplastic change. HPV testing is not usually done, as HPV is known o be the cause of the particular change. A high risk subtypeof HPV is known to be present. Further investigation with coloscopy is usually recommended. Colposcopy is discussed in more detail below.

2. HSIL (stands for "high grade squamous intra-epithelial lesion")

With this kind of PAP, the cells meet the criteria for moderate to severe precancerous change, and the chances of the lesion progressing on to cancer if untreated are higher. Once again, testing for high risk subtypes of HPV is not routinely done, since we already know this is present. Further investigation with colposcopy is recommended in this situation as well.

3. ASCUS (stands for "atypical squamous cells of undetermined significance")

This is the most common type of abnormal PAP. About 3% of PAPs return with this diagnosis. This diagnosis is given when the cells on the PAP do not clearly meet the criteria for being abnormal, but also do not clearly meet the criteria for being normal. It is the pathologist's way of saying "I'm not quite sure". At our clinic, we order PAPs in such a way that a test for high risk HPV is automatically done when the PAP is given an ASCUS diagnosis. That allows us to know which PAPs we need to be concerned about, and investigate further with colposcopy.

4. AGUS (stands for "atypical glandular cells of undetermined significance)

This is the least common of the four main types of abnormal PAPs. It is not always caused by HPV. It always needs further investigation so we don't do HPV testing to see who needs colposcopy. Sampling is usually done of both the cervix and the uterus, since abnormal glandular cells from the uterus can also have this appearance.

FURTHER INVESTIGATION - COLPOSCOPY

Most abnormal PAPs are usually investigated further with the use of COLPOSCOPY. A colposcope is a large magnifying glass used to examine the cervix in greater detail than can be seen with the naked eye. During a colposcopic exam, a speculum is placed, just like during a normal pelvic exam. Acetic acid (vinegar) is applied to the cervix. Dysplastic areas of the cervix (as well as normal areas undergoing usual cell turnover) turn a whitish color. This is one of the changes that can be observed with a colposcope. We also look for abnormal blood vessel patterns by using a green filter with the colposcope light, and we apply an iodine stain that is picked up by most normal tissue, but not by dysplasic areas of the cervix.

These changes help the gynecologist to determine the worst appearing sites on the cervix and these are usually biopsied with a small instrument that grasps and removes a very small amount (about a millimeter diameter) of tissue to send to the pathologist. Although this seems like a small amount of tissue, it represents many more cells than a PAP, so gives the pathologist a much clearer picture of what is happening. Often the cervical canal leading to the uterus (the endocervical canal) is sampled as well, to be sure there is no lesion higher up in the cervix where it cannot be easily seen with the colposcope. Most people tolerate the biopsies very well. They usually feel like a mild menstrual cramp, and this sensation passes a few seconds after the biopsy has been taken.