Cervical cytology is the microscopic study of cells taken from the cervix, the lower part of the uterus that connects to the vagina. Its primary function is as a screening tool to detect precancerous or cancerous cells at an early stage. This examination identifies cellular abnormalities that could develop into cervical cancer, allowing them to be found when they are more easily treatable. By identifying these issues before symptoms appear, cervical cytology is a preventative health measure for anyone with a cervix.
The Purpose of Cervical Screening
The purpose of cervical screening is to prevent cervical cancer by identifying abnormal cellular changes before they become malignant. This process is not a test for cancer, but a method to detect its precursors. The screening looks for changes in cervical cells that, if left untreated, could develop into cancer over several years. Early detection through regular screening is credited with a significant decrease in deaths from cervical cancer.
A key part of this screening process is its connection to the Human Papillomavirus (HPV). Nearly all cases of cervical cancer are caused by persistent infections with high-risk types of HPV, a common virus spread through sexual contact. While most HPV infections are cleared by the body’s immune system, some high-risk strains can persist and lead to changes in cervical cells. The screening test is designed to find these cellular changes, acting as a safeguard by monitoring for the consequences of the virus.
The Sample Collection Process
A sample of cervical cells is collected during a procedure known as a Pap smear or Pap test. The process involves a healthcare provider inserting a speculum into the vagina. This instrument gently opens the vaginal walls, allowing the provider to see the cervix. The speculum is typically made of plastic, and a new one is used for each test to ensure sterility.
Once the cervix is visible, a small, soft brush or a tiny spatula is used to gently scrape a sample of cells from its surface. This part of the procedure may cause a feeling of pressure or mild discomfort, but it is usually brief. Patients are encouraged to communicate with their provider if they experience pain, as adjustments can be made to increase comfort. The patient can ask to stop the procedure at any time.
After collection, the cell sample is preserved for laboratory analysis using one of two primary methods. In conventional cytology, the cells are smeared directly onto a glass slide. With liquid-based cytology, the sample is rinsed into a vial of preservative liquid, a method that also allows for high-risk HPV testing from the same sample.
Interpreting the Results
After laboratory analysis, results are categorized to describe the findings. A “negative for intraepithelial lesion or malignancy” result, also called a normal result, means no abnormal cells were detected. This is the most common outcome and indicates a very low risk of developing cervical cancer.
The most frequent abnormal finding is “Atypical Squamous Cells of Undetermined Significance” (ASC-US). This result means some cells appear slightly different from normal, but the changes are not distinct enough to be classified as precancerous. The cause for these cellular changes is often unclear and can be related to factors other than HPV, such as inflammation.
A “Low-Grade Squamous Intraepithelial Lesion” (LSIL) indicates that mild, low-grade cellular changes have been identified. These changes are most often caused by an HPV infection. In many cases, the immune system will clear the infection, and the cells will return to normal without treatment.
A “High-Grade Squamous Intraepithelial Lesion” (HSIL) is a more serious finding that signifies moderate to severe changes in the cervical cells. These cells have a higher likelihood of progressing to cancer if not removed and point to a persistent HPV infection requiring intervention. A less common result, “Atypical Glandular Cells” (AGC), indicates abnormalities in the glandular cells of the cervix, which also necessitates further evaluation.
Recommended Next Steps After Results
Follow-up actions are tied to the specific findings. For a negative or normal result, the recommendation is to continue with routine screening at the recommended interval, typically every three to five years depending on age and history. This interval is considered safe because it takes many years for significant cell changes to progress to cancer.
If the result is ASC-US, follow-up may involve a repeat cytology test in one year to see if the cellular changes have resolved. Another option is to test the sample for high-risk HPV. If the HPV test is negative, routine screening can resume; if it is positive, a more detailed examination is recommended.
For results of LSIL, HSIL, or AGC, the standard next step is a referral for a colposcopy. During this procedure, a specialist uses a magnifying instrument called a colposcope to get a close-up view of the cervix and examine any areas that appeared abnormal. If suspicious areas are seen, a biopsy, which is a small sample of tissue, may be taken for further analysis. This step helps determine the severity of the changes and guides necessary treatment to remove the abnormal cells.