The Bethesda System (TBS)

Topic Overview

The Bethesda system (TBS) was developed by the United States National Cancer Institute (NCI) to provide more detailed information about Pap test results. When lab specialists examine cervical cells, they use this system to report the lab results to doctors.

Your doctor gets the report from the lab. The report tells your doctor if the cell sample was good enough to be evaluated. It also lets your doctor know if the cells were normal or abnormal or if there was an infection present.

If the cells were abnormal, they are put in categories, or typed, based on how severe the problem is.

• Cells that show minor changes but the cause is unknown may be typed as ASC-US or ASC-H. ASC-US stands for atypical squamous cells of undetermined significance. ASC-H stands for atypical squamous cells that cannot exclude high-grade squamous intraepithelial lesion.
• Cells that show definite minor changes but aren't likely to become cancer may be typed as LSIL. It stands for low-grade squamous intraepithelial lesions.
• Cell changes that are more severe and are more likely to become cancer may be typed as HSIL or AGC. HSIL stands for high-grade squamous intraepithelial lesions. AGC stands for atypical glandular cells.