Abnormal Pap Smears - What Does it Mean?

Understanding Dysplasia, ASCUS, SIL, and CIN

swab for Pap smear
What does your abnormal Pap smear result mean?. Istockphoto.com/Stock Photo©DETart21

If you've been told you have an abnormal Pap smear, you're probably feeling frightened. What does this mean for you? What do all of those confusing terms mean? What is the next step? Could you have cancer?

Abnormal Pap Smears - Definition

An abnormal Pap smear simply means that a scraping taken from your cervix (a Pap smear) is abnormal. An abnormal Pap smear does not automatically mean that you are at risk for developing cervical cancer.

There are a multitude of reasons a Pap smear may be abnormal, and these causes can span the spectrum from mild inflammation to cancer. What an abnormal test tells us is simply that your cervix needs to be evaluated further—even if that only means repeating a Pap smear in 3 years. The next step following a Pap smear depends on the specific description on your pathology report. We will take a look at what you may hear when you get your results.

Purpose of Pap Smears

Pap smears are used to detect the presence of abnormal cervical cells which could, in time, progress to cancer. While there is debate over the benefit of some screening tests, Pap smears have clearly saved lives. Cervical cancer was once a leading cause of cancer deaths in women in the United States. That said, around 12,000 women will be diagnosed with cervical cancer each year, and around 4,000 will die from the disease.

How Common are Abnormal Pap Smears?

Abnormal Pap smears are very common.

The CDC estimates that 3 million women have abnormal Pap smear results each year. (If this makes you anxious, compare this to the 4,000 women who die from cervical cancer each year, and it's clear that most abnormal Pap smears are frightening but not serious.) Of these women, ASCUS (see below) is the most common listed abnormality, and in these women, at least 75 percent have no abnormal cervical cells on further testing.

Abnormal Pap Smear Results - Medical Terminology Listed

Before going into the specifics on abnormal Pap smears, it's helpful to simply define some of the terms you may hear. These will all be discussed in greater depth below. Note that some of these descriptions are used for Pap smear results, whereas others, such as CIN are used only on cervical biopsy reports.

  • Dysplasia refers to abnormal cells on a Pap smear. On it's own, dysplasia could mean anything from very mild (and meaningless changes) to early cancer. Dysplasia may be referred to as low grade, moderate grade, severe grade
  • ASCUS stands for atypical cells of undetermined significance on a Pap smear
  • SIL stands for squamous intraepithelial lesion on a Pap smear
  • LGSIL low grade squamous intraepithelial lesion on a Pap smear
  • HGSIL high grade squamous intraepithelial lesion on a Pap smear
  • CIN stands for carcinoma in situ - CIN is reported on a cervical biopsy specimen, not on Pap smears
  • AGC stands for atypical glandular cells on a Pap smear

Normal Cells, Precancerous Cells, and Cancer Cells

Before going into depth describing the terminology of abnormal Pap smears, it's helpful to know a little about the natural history of cervical cancer.

Cervical cancer is a cancer of epithelial cells. With cancers of epithelial cells (unlike some cancers) there is usually a precancerous stage. Often when cells are caught at this early precancerous stage, treatment can prevent them from progressing on to become cancer cells.

Cells in the cervix begin as normal cells. When exposed to carcinogens in the environment and other factors, changes occur in the cells. The first step is dysplasia. Most cells that become "dysplastic" do not become more abnormal. When cells do become more abnormal they are referred to as precancerous cells. Precancerous cells may or may not go on to become cancer.

The earliest stage of cancer iscarcinoma in situ. With carcinoma in situ the cells are considered to be cancer cells, but they have not yet spread beyond something called the basement membrane. In other words, they are not invasive. Since carcinoma in situ is not invasive—it is also called stage 0 disease—it should theoretically be 100 percent curable.

When carcinoma in situ progresses—when it spreads through the basement membrane—it is then referred to as cervical cancer. Stages I to IV of cervical cancer are considered invasive, not because they have spread (which in the early stages it hasn't) but because the cells have spread beyond the basement have have the potential to spread further. (Learn more about the differences between normal cells and cancer cells.)

Abnormal Pap Smears - Dysplasia, ASC, SIL, and CIN

The following terms are used to describe abnormalities on a Pap smear or biopsy. Note again that many of these terms describe findings on a Pap smear whereas CIN is used to describe findings on a biopsy. Following these descriptions we will list the current guidelines for next steps based on these terms.


The term dysplasia is a catch-all term which simply means that abnormal appearing cells are seen on a Pap smear. Depending on the degree of dysplasia, your results may correspond to one of the more specific descriptions listed below. Dysplasia does not mean that precancerous cells or cancerous cells are present, or even that there is concern these will develop. Dysplasia may be due to these changes, or may simply reflect a vaginal infection or even menopausal changes in the cervix. When mentioned, dysplasia may be subdivided into low-grade, moderate grade, and high grade dysplasia.

ASC Pap Smears (ASCUS and ASC-H)

ASC stands for abnormal squamous cells. It is the most common type of abnormality on Pap smears.

  • ASCUS - ASCUS stands for abnormal squamous cells (cells that look like fish scales) of undetermined significance on a Pap smear. Instead of being a normal Pap smear, or an abnormal Pap smear, ASCUS stands somewhere in the middle; it is indeterminate. ASCUS means that the squamous cells are slightly abnormal but the changes do not suggest the presence of precancerous cells. This result could be due to a vaginal infection or most often, due to HPV infection. Three out of four women with an ASCUS result on a Pap smear have no abnormal cervical cells on a closer look.
  • ASC- H - In contrast to ASCUS, ASC-H raises concern that there may be high grade intraepithelial cells (HSIL) present. Some cells are abnormal and there is a possibility that some cells are precancerous.

SIL Pap Smears

SIL stands for squamous intraepithelial lesion. SIL cells may be precancerous. They are graded based on the size, shape, and other features of the cells.

  • LSIL or LGSIL stands for low grade intraepithelial cells. These cells are mildly abnormal, often due to the presence of an HPV infection. Many of these HPV infections go away without any treatment.
  • HSIL or HGSIL stands for high grade intraepithelial cells. Changes in these cells may be associated with precancerous or cancerous cells (they are very abnormal). and further evaluation or treatment is needed.
  • Atypical cells cannot exclude HSIL - Sometimes a report carries this description, which is similar to ASC-H.

AGC Pap Smears

AGC stands for atypical glandular cells. These glandular cells may arise in the inner cervical opening or in the uterus. When AGC are present, the source of the cells (inner cervix or uterus) needs to be determined. These cells suggest the possibility of precancerous or cancerous cells and always need to be evaluated.

CIN on Biopsy

Carcinoma in situ, or CIN, is a description used on on cervical biopsy reports and not on Pap smears. A biopsy is able to determine actual changes in cervical cells (with a Pap smear, only scattered cells are visualized.) CIN II and CIN III (moderate and high) may be considered precancerous

CIN can be described relative to Pap smear reports in the following way:

  • CIN I often corresponds to LSIL or mild dysplasia
  • CIN II often corresonds to HSIL or moderate dysplasia (these abnormal cells make up roughly half of the thickness of the surface lining)
  • CIN III often corresponds to severe dysplasia or carcinoma in site (the entire surface of the surface cell layer (epithelium) is composed of abnormal cells, but these have not spread below the surface, below the basement membrane)

Squamous Cell Carcinoma and Adenocarcinoma Cells

If cancer cells are found on a Pap smear or biopsy, definitive treatment to remove the cancerous cells as well as surrounding cells is needed.

Comparison of Descriptions

CIN can be described relative to Pap smear reports in the following way:

  • CIN I often corresponds to LSIL or mild dysplasia
  • CIN II often corresonds to HSIL or moderate dysplasia (these abnormal cells make up roughly half of the thickness of the surface lining)
  • CIN III often corresponds to severe dysplasia or carcinoma in site (the entire surface of the surface cell layer (epithelium) is composed of abnormal cells, but these have not spread below the surface, below the basement membrane)

HPV Types and Testing

If you have had an abnormal Pap smear, it's likely that your doctor also performed HPV testing to test for human papillomavirus (HPV) yet this can be confusing as well. One area of confusion is based on age. Women older than age 30 are often evaluated differently than women less than age 30. The type of testing is also confusing.

Types of HPV include:

  • High risk HPV - High risk HPV include strains that may lead to the development of cervical cancer (and vaginal, penile, and head and neck cancer.) These are also called oncogenic HPV and include HPV 16, 18, 31, 33, 35, 45, 52, 58, and 59.
  • Low risk HPV - Low risk HPV strains are considered non-oncogenic HPV. Infections with these strains does not lead to cancer, but cancer cause vaginal warts. Two of these include HPV 6 and 11.

There are over 50 strains of HPV, yet only a few of these cause cervical cancer, the most common being HPV 16 and HPV 18. Learn more about the differences between low risk and high risk HPV.

Tests for HPV include:

  • HPV testing refers to a test looking for evidence of any strains of HPV
  • HPV typing - HPV typing tests for the presence of cancer causing strains of HPV, at least HPV 16 and HPV 18.

It can be helpful to define a few terms used as well.

  • Co-testing for HPV refers to doing both a Pap smear and HPV test at the same time during a routine Pap smear.
  • Reflex HPV - This term is used when ordering a test for high-risk HPV on the same sample as the Pap smear.

Cervical Cancer Screening and Follow-Up of Abnormal Results - Next Steps in Management

The current cervical cancer screening guidelines are based on age and other factors. For those who have abnormal results, as noted above, the following table lists current recommended next steps based on age and HPV status.

Possible approaches include:

  • Watchful waiting
  • Repeat Pap smears in 12 months or 3 years
  • HPV co-testing or reflex testing
  • Colposcopy and cervical biopsy of any abnormal appearing areas (a colposcopy is like a Pap smear with a magnifying glass)
  • Endocervical sampling (endocervical curettage)
  • Endometrial sampling (if there is a possibility that the cells are of uterine origin rather than uterine cervix origin)
  • Definitive treatment such as cryosurgery, LEEP, or cone biopsy

Follow-Up Tests for Abnormal Pap Smears

  •  Age 21-24Age 25-29Over 30, HPV negativeOver 30, HPV positive

    Preferred - Repeat Pap 12 months

    Acceptable - Relfex HPV

    Preferred - Reflex HPV

    Acceptable - Repeat Pap 12 months

    Repeat co-testing (Pap + HPV) in 3 yearsColposcopy
    LSILRepeat Pap in 12 monthsColposcopy

    Preferred - Repeat Pap in 12 months

    Acceptable - Colposcopy

    HSILColposcopyImmediate excisional treatment** or colposcopyImmediate excisional treatment or colposcopyImmediate excisional treatment or colpscopy
    AGC*Dependent on AGC subcategoryDependent on AGC subcategoryDependent on AGC subcategoryDependent on AGC subcategory

    * Tests for AGC subcategories include colposcopy, endocervical sampling, and endometrial sampling. **Cryosurgery, LEEP, or cone biopsy.


American College of Obstetrics and Gynecology. Abnormal Cervical Cancer Screening Test Results. Updated 01/2016. http://www.acog.org/Patients/FAQs/Abnormal-Cervical-Cancer-Screening-Test-Results

Kim, J., Kim, T., Lee, I., and S. Hong. Associations Between Sexually Transmitted Infections, High-Risk Human Papillomavirus Infection, and Abnormal Cervical Pap Smear Results in OB/GYN Patients. Journal of Gynecologic Oncology. 2016. 27(5):e49.

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