The surface of a woman's cervix is made up of cells known as squamous cells. In some cases, some cells may become abnormal; these are known as atypical squamous cells, or ASC. These abnormal cells may be caused by a variety of issues, some of more concern than others.
Atypical squamous cells are typically discovered during a routine Pap smear. This is a gynecological test where a doctor collects and examines cells from the cervix to determine if they are healthy. If any cells appear abnormal, this is referred to as dysplasia, which may be a precursor to cancer. In these cases, the doctor will perform further tests to find the root cause of the issue.
There are two categories of abnormal squamous cells; the first is known as ASC-US, or atypical squamous cells with uncertain significance. This means there are some minor changes in a portion of the cells, but the cause is not immediately clear. ASC-US is generally not considered to be dysplasia, as the abnormalities in the cells are very minimal. They may be the result of several relatively minor issues, including a yeast infection, hormonal changes, or the use of certain medications.
Pap results that fall under the ASC-US category typically are not an immediate cause for concern. A test for the human papillomavirus, or HPV, may be useful to determine if this is the cause, as it is often responsible for abnormal cells, plus it may also later contribute to cancer, so early diagnosis is desirable. If the woman is negative for HPV, a second Pap smear may be performed after several months to see if the atypical squamous cells are still present. Once a woman has had two normal Pap smears, she can return to regular routine exams. If the second Pap is again ASC-US, further tests will probably be required.
The second type of atypical squamous cell is known as ASC-H. The H means that the results suggest the possibility of a high-grade squamous intraepithelial lesion. These types of cells are extremely abnormal and may be precancerous, so further testing should be performed right away. The doctor will typically order a colposcopy, where the cells of the cervix are coated with a solution and then examined using an instrument called a colposcope. A biopsy may also be necessary to remove a sample of tissue for laboratory examination.