Human Papillomavirus (HPV) is a common group of viruses responsible for nearly all cases of cervical cancer. This infection is also strongly linked to cancers of the anus, vagina, vulva, penis, and oropharynx (throat). Before these cancers develop, the virus typically causes slow-growing, precancerous changes in the tissue. Detecting and treating these cellular changes, known as dysplasia, is highly effective at preventing the progression to invasive cancer.
Understanding Precancerous Lesions
A precancerous lesion is abnormal cell growth resulting from persistent infection with high-risk HPV types. These changes are classified using two main terminologies: Cervical Intraepithelial Neoplasia (CIN) and Squamous Intraepithelial Lesion (SIL). CIN uses a three-tiered grading system (CIN 1, CIN 2, and CIN 3) based on how much of the tissue layer is affected. Clinicians also use the two-tiered Bethesda System, grouping these changes into Low-Grade SIL (LSIL) and High-Grade SIL (HSIL).
The distinction between these grades determines the management plan. Low-grade lesions (CIN 1 or LSIL) affect only the superficial third of the tissue layer. These lesions frequently resolve on their own, as the body’s immune system often clears the HPV infection. High-grade lesions (CIN 2, CIN 3, or HSIL) involve two-thirds or more of the tissue layer and carry a significantly higher risk of progression to invasive cancer, requiring active medical intervention.
Initial Screening for Abnormalities
Routine screening tests identify precancerous lesions. The traditional Papanicolaou (Pap) test is a cytology-based screening tool that involves collecting cells from the cervix. These cells are examined under a microscope to detect abnormal morphology, which suggests the presence of dysplasia.
The HPV test is a virology-based test that looks for the presence of high-risk types of the virus itself, such as HPV 16 and 18, which cause the majority of HPV-related cancers. Current guidelines often favor primary HPV testing or co-testing, which combines both the Pap test and the HPV test from a single cell sample. Co-testing provides a more comprehensive risk assessment, as a negative result on both tests offers strong reassurance of a very low risk of developing cancer in the near future.
This combined strategy is especially important for individuals over the age of 30, for whom the risk of a transient HPV infection is lower. An abnormal result from either test does not mean a person has cancer, but rather indicates an elevated risk that warrants further investigation and diagnostic procedures.
Confirming the Diagnosis
When screening tests return an abnormal result, the next step is a colposcopy. This examination uses a colposcope—a magnifying instrument with a bright light—to visualize the cervix and the transformation zone at high magnification. During the procedure, the clinician applies a mild acetic acid solution, which causes abnormal tissue to temporarily turn white, highlighting the precise location and extent of the lesions.
If abnormal areas are identified, a directed biopsy is performed, taking a small tissue sample from the suspicious spot. This specimen is sent to a pathology lab for definitive grading (CIN 1, CIN 2, or CIN 3), providing the diagnosis needed to formulate a treatment plan.
If the entire area of concern, particularly the upper cervical canal, cannot be adequately viewed, an Endocervical Curettage (ECC) may be performed. This involves using a curette to gently scrape and collect a sample of the tissue lining the canal. ECC ensures that no high-grade lesions are missed higher up in the cervix before proceeding with any ablative treatment.
Treatment Procedures
Management is determined by the grade of dysplasia. Low-grade lesions (CIN 1/LSIL) are typically managed conservatively through observation or watchful waiting, as the majority regress spontaneously when the body clears the HPV infection. Intervention may be considered if a low-grade lesion persists for two years or more.
High-grade lesions (CIN 2/3, HSIL) and persistent low-grade lesions require active treatment, categorized as ablative or excisional. Ablative procedures, such as cryotherapy or laser ablation, destroy the abnormal tissue in place by freezing or burning it. A limitation of these methods is that they do not provide a tissue specimen for pathological confirmation of clear margins.
Excisional procedures are the preferred intervention for high-grade lesions because they physically remove the affected tissue for laboratory analysis. The most common excisional technique is the Loop Electrosurgical Excision Procedure (LEEP), which uses a thin, electrified wire loop to shave off the abnormal area. This quick, in-office procedure simultaneously cuts the tissue and seals the blood vessels, resulting in minimal bleeding.
The Cold Knife Conization (CKC) procedure is a more complex excisional method that uses a surgical scalpel to remove a cone-shaped piece of tissue. CKC is usually performed in an operating room under general anesthesia and is often reserved for cases where the lesion extends high into the cervical canal or when a glandular abnormality is suspected. A slight risk associated with any excisional procedure is the potential for cervical shortening or weakening, which may increase the risk of preterm delivery in future pregnancies.
Long-Term Monitoring and Prevention
Following successful treatment, a robust surveillance plan monitors for recurrence. This follow-up, often referred to as “test of cure,” is crucial because treated individuals remain at an elevated risk of developing new or recurrent lesions for many years. Initial surveillance typically involves a combination of HPV and Pap co-testing at short intervals (e.g., every six to twelve months) to confirm the elimination of the high-risk HPV.
For patients treated for high-grade lesions (CIN 2 or CIN 3), continued surveillance with co-testing every three years is recommended for at least 25 years. This long-term strategy ensures any new cellular changes are detected early.
The HPV vaccine plays a significant role in long-term prevention, even for individuals who have already been treated. Studies suggest that receiving the HPV vaccine after treatment for CIN may reduce the risk of lesion recurrence by preventing future infections from the high-risk HPV types covered by the vaccine. Vaccination serves as a powerful protective measure alongside surveillance to reduce the risk of HPV-related cancers.