A Pap smear, or Pap test, is a medical screening procedure designed to detect changes in cervical cells that could potentially lead to cancer. Named after Dr. George Papanicolaou, the test involves examining these cells under a microscope. Identifying cellular abnormalities early allows for timely intervention, effectively preventing the progression to cervical cancer. This screening is a fundamental part of preventive healthcare, relying heavily on detailed visual analysis performed by laboratory technicians and pathologists.
The Purpose and Process of Screening
The Pap smear is a screening tool designed to find cellular abnormalities before they cause symptoms or become invasive cancer. It is not a diagnostic test for cancer itself, but an early warning system for precancerous changes. These changes, known as dysplasia, typically develop over several years, giving the screening a broad window for detection and treatment.
The procedure begins when a healthcare provider collects cells from the cervix using a small brush or spatula. This collection is generally done during a routine pelvic examination. Patients should avoid douching, using vaginal medicines, or having intercourse for about two days before the test, as these actions can obscure the cells needed for an accurate reading.
After collection, the cells are immediately preserved. Modern practice uses liquid-based cytology (LBC), placing the sample into a vial of preservative liquid. LBC minimizes contamination from blood or mucus, helping the lab create a cleaner, more uniform layer of cells for examination and reducing the chance of an unsatisfactory sample.
What Lab Technicians Look For
Once the sample reaches the laboratory, a cytotechnologist prepares the cells, often using an automated process to create a monolayer—a thin, even layer of cells—on a glass slide. This preparation is then stained to highlight the cellular structures before the technician examines it under a microscope. The technician’s job is to visually compare the collected cells to the appearance of normal, healthy cervical cells.
Normal cervical cells are typically flat, uniform, and contain a small nucleus relative to the overall cell size. The technician specifically looks for two main types of normal cells: squamous cells, which cover the outer part of the cervix, and glandular cells, which line the inner canal. An abnormal finding, or dysplasia, is characterized by noticeable changes in the cell’s appearance.
These abnormal cells may show variation in size and shape, a feature known as pleomorphism. The nucleus of the abnormal cell is often enlarged, darker than normal (hyperchromatic), and occupies a disproportionately large area of the cell’s cytoplasm. These atypical cells look disorganized and suggest infection by the human papillomavirus (HPV), the cause of nearly all cervical cancers.
Understanding Your Pap Smear Results
The findings from the visual analysis are reported using the Bethesda System, which classifies the results into standardized categories. A “Negative for Intraepithelial Lesion or Malignancy” (NILM) result means the cells look normal and no signs of precancer or cancer were observed. When abnormalities are found, they fall into categories that indicate the level of cellular change.
One of the most common abnormal results is Atypical Squamous Cells of Undetermined Significance (ASCUS). This means some cells look slightly irregular, but the changes are not distinct enough to be classified as a definitive precancerous lesion. This mild finding is often related to a temporary infection and frequently returns to normal on its own.
More defined precancerous changes are classified as Squamous Intraepithelial Lesions (SIL). Low-Grade SIL (LSIL) shows mild cellular changes, which are characteristic of a current HPV infection. High-Grade SIL (HSIL) represents more severe, definite precancerous changes, and these lesions have a higher likelihood of progressing to cancer if they are not treated.
Pap test results are often paired with an HPV test, especially for individuals over 30, because HPV is the underlying cause of the cellular changes. A result of Atypical Glandular Cells (AGC) refers to less common abnormalities in the glandular cells of the inner cervix, often requiring further investigation due to the potential for a more serious underlying issue.
Necessary Follow-Up Procedures
An abnormal Pap result does not automatically mean a cancer diagnosis; it signals the need for closer monitoring or intervention. The specific next step is determined by the severity of the abnormality and the patient’s age and HPV status. For mild changes like ASCUS or LSIL, particularly in younger individuals, the initial recommendation may be watchful waiting and a repeat Pap test in six to twelve months, as these low-grade changes often resolve spontaneously.
If the result is HSIL or if a low-grade abnormality persists, the next procedure is typically a colposcopy. This in-office examination uses a specialized magnifying instrument, the colposcope, to provide a lighted, detailed view of the cervix. During the procedure, a mild vinegar solution may be applied to the cervix to temporarily highlight any areas of abnormal tissue, making them easier to see.
If the colposcopy reveals suspicious areas, the provider will perform a biopsy, taking a small tissue sample for a pathologist to analyze. If the biopsy confirms moderate to severe precancerous lesions (often classified as CIN 2 or CIN 3), treatment is recommended to remove the affected tissue. Common excisional procedures include the Loop Electrosurgical Excision Procedure (LEEP) or cryotherapy, which remove or destroy the abnormal cells to prevent cancer development.