Receiving an abnormal result from a cervical screening, or Pap test, can be unsettling, but a finding of Low-Grade Squamous Intraepithelial Lesion (LSIL) is extremely common. This result means that minor cell changes were detected on the surface of the cervix, but it is not a diagnosis of cancer. LSIL represents a frequent, usually temporary condition that rarely develops into a serious health problem. Medical professionals regard this precursor lesion with careful monitoring rather than immediate aggressive intervention. Understanding the biology and the recommended follow-up protocol is the first step in managing this common diagnosis.
Defining Low-Grade Squamous Intraepithelial Lesion
The term Low-Grade Squamous Intraepithelial Lesion describes changes observed in the squamous cells that form the thin, protective outer layer of the cervix. When a pathologist examines the cells collected during a Pap test, LSIL indicates that the cells show slight abnormalities in their size, shape, or organization. These minor alterations are sometimes referred to as mild dysplasia.
The classification “intraepithelial” clarifies that the abnormal changes are strictly confined to the surface layer of the tissue. These cells have not penetrated the underlying layers or grown into the deeper cervical tissue. LSIL is therefore categorized as a non-invasive, precancerous condition, meaning the potential for progression to cancer is low.
The “low-grade” designation distinguishes this finding from a High-Grade Squamous Intraepithelial Lesion (HSIL), which involves more significant cellular changes. While HSIL includes moderate to severe dysplasia and has a higher risk of progressing, LSIL represents the mildest form of cellular abnormality.
The Connection to HPV
Virtually all cases of LSIL are caused by an infection with the Human Papillomavirus (HPV), a highly common sexually transmitted infection. HPV is a group of over 200 related viruses, and infection is so widespread that most sexually active individuals will contract at least one strain. The virus infects the squamous cells, triggering the minor changes identified as LSIL on a Pap test.
The immune system is effective at fighting off HPV, and the majority of infections clear spontaneously within one to two years. When the virus is eliminated, the abnormal cellular changes typically revert to normal. This natural course is why LSIL is considered a transient finding rather than a permanent condition.
HPV strains are classified into low-risk and high-risk types based on their potential to cause cancer. Although LSIL is a low-grade finding, it can be associated with high-risk HPV types, such as HPV 16 and 18, which are responsible for the vast majority of cervical cancers. The presence of a high-risk HPV type alongside an LSIL result is a factor that medical providers monitor closely.
Next Steps and Management
The standard approach to managing LSIL centers on observation, often called “watchful waiting,” due to the high likelihood of spontaneous regression. Clinical studies show that LSIL lesions resolve on their own in a significant number of cases, with regression rates reported to be around 61% within 12 months for young individuals. The immune response clears the underlying HPV infection, allowing the cervical cells to normalize.
For many patients, especially those under 25, initial management involves repeating the Pap test and HPV co-testing after a period, typically 12 months. This surveillance strategy helps confirm whether the infection has cleared and the LSIL has resolved, avoiding unnecessary procedures. Immediate aggressive treatment is avoided in these low-risk scenarios to prevent potential side effects, such as premature labor in future pregnancies.
If the repeat screening continues to show an LSIL result or is positive for a high-risk HPV type, a healthcare provider will likely recommend a colposcopy. This procedure is a detailed visual examination of the cervix using a specialized magnifying instrument. The clinician applies a solution to highlight abnormal areas, and the physician may take small tissue samples, called biopsies, from any suspicious areas to determine the actual grade of the lesion.
A referral for colposcopy is often recommended immediately for patients over the age of 25 who test positive for specific high-risk HPV types, such as HPV 16 or 18, or for those whose LSIL has persisted for two years or more. This is because a persistent lesion carries a higher risk of progression. The goal of this pathway is to identify the small percentage of cases where the LSIL may have progressed to a higher-grade lesion requiring treatment.