When a cervical screening, commonly known as a Pap test, returns an abnormal result, it can be confusing. One of the most frequent findings is Atypical Squamous Cells of Undetermined Significance (ASCUS). This result indicates that the cells collected from the cervix show minor changes from what is considered typical. Understanding this finding is the first step in following the appropriate medical guidance.
Understanding Atypical Squamous Cells of Undetermined Significance
The acronym ASCUS represents the mildest category of abnormal cell change reported on a Pap test. It is not a diagnosis of cervical cancer, but a finding that requires further clarification. The term “atypical” means that the squamous cells lining the outer part of the cervix look slightly different or irregular under the microscope.
The phrase “of undetermined significance” means the pathologist could not determine a definitive cause for the cellular changes. These minor variations may be temporary, perhaps caused by inflammation, an infection, or hormonal fluctuations. However, they could also be the first sign of a persistent infection that may lead to precancerous changes. ASCUS serves as a flag that additional testing is necessary to assess the level of risk.
The Primary Driver of ASCUS: Human Papillomavirus
The most common underlying cause of cellular changes resulting in an ASCUS finding is infection with the Human Papillomavirus (HPV). This is a very common sexually transmitted infection. The body’s immune system typically clears the infection within one to two years, and the cervical cells return to normal.
When an HPV infection persists, particularly with certain high-risk types, it can lead to sustained changes in the cervical cells. While there are over 200 types of HPV, only about 14 are classified as high-risk and are responsible for nearly all cases of cervical cancer. Low-risk HPV types do not cause cancer. Because persistent high-risk HPV infection is the condition most likely to cause precancerous changes, follow-up testing focuses on detecting its presence.
What Happens After an ASCUS Result? Management and Follow-Up
The next step following an ASCUS result is determined by current medical guidelines, which focus on risk stratification, often utilizing HPV testing. The preferred approach for women aged 25 to 65 is to perform a reflex test for high-risk HPV types using the same sample collected for the Pap test. This co-testing helps determine if the atypical cells are linked to the virus that causes most cervical precancers.
If the high-risk HPV test is negative, the risk of developing a serious lesion is very low, similar to that of a person with a completely normal Pap test. In this scenario, the patient will return to routine cervical cancer screening, usually in three years. If the high-risk HPV test is positive, the patient is referred for a colposcopy, which is a procedure where the healthcare provider uses a magnifying device to closely examine the cervix.
For younger patients, specifically those aged 21 to 24, immediate colposcopy is often avoided due to the high likelihood that HPV infections and minor cell changes will clear on their own. Instead, management typically involves repeating the Pap test in 12 months. If the repeat test is still abnormal, or if the abnormality is more severe, further evaluation is then pursued. Regular follow-up appointments are the primary way to ensure any persistent changes are addressed before they can progress.