A Pap test screens for changes in cervical cells. While an abnormal result can cause concern, these findings are often not serious. Low-Grade Squamous Intraepithelial Lesion (LSIL) is a common type of abnormal Pap test result. This article explains what LSIL means, its frequency, underlying cause, and typical next steps.
What LSIL Means
LSIL stands for Low-Grade Squamous Intraepithelial Lesion. Squamous cells are the thin, flat cells forming the surface lining of the cervix, which are the primary focus of a Pap test.
“Intraepithelial” means cellular changes are confined to this surface layer, not spreading deeper into cervical tissue. The “low-grade” designation signifies mild cellular changes. These mild changes often resolve without intervention. LSIL is not cancer; it represents a mild alteration in cells that warrants monitoring.
How Often LSIL Occurs
LSIL is considered one of the most frequently encountered abnormal Pap test results. Data indicates that LSIL makes up approximately 1.4% to 1.6% of all cytology results. The occurrence of LSIL varies across different age groups.
The highest reporting rate of LSIL, around 3.6%, is observed in women younger than 20 years of age. This rate tends to gradually decrease as women get older. These statistics highlight that LSIL is a relatively common finding, particularly among younger individuals.
The Underlying Cause and What It Signifies
LSIL is almost always attributed to an infection with the Human Papillomavirus (HPV). HPV is a common virus, and the presence of LSIL indicates an active HPV infection affecting the cervical cells.
Studies show that a significant majority of women with an LSIL diagnosis test positive for high-risk HPV types, with rates often exceeding 75%. While HPV infection is widespread, most infections are temporary, with the body’s immune system clearing the virus within two years in 70% to 80% of cases. This natural clearance often leads to the spontaneous resolution of LSIL, with a regression rate of nearly 50% back to normal. LSIL itself is not cancerous, and only a small fraction of cases progress to more significant changes or invasive cancer.
What Happens After an LSIL Result
Following an LSIL Pap test result, medical management typically focuses on careful monitoring due to the high likelihood of spontaneous resolution. For women aged 21 to 24, repeat cytology is often recommended in 12 months. This approach acknowledges that low-grade lesions frequently clear naturally in this age group.
For individuals aged 25 and older, or if an LSIL result persists, or if high-risk HPV co-testing is positive, a colposcopy may be recommended. A colposcopy involves a magnified examination of the cervix, allowing the healthcare provider to visualize the area more closely and take biopsies if suspicious tissue is identified. Adherence to these follow-up recommendations is important to ensure any changes are appropriately managed.