Pap Test: Classification of Cell Changes

Topic Overview

Cervical cell changes are classified according to their degree of abnormality using the Bethesda system (TBS). Further evaluation decisions are guided by the kinds of changes seen in the cells.

Minor cell changes

Minor cervical cell changes are also called:

• Atypical squamous cells (ASC). ASC is further classified as:
  • ASC of undetermined significance (ASC-US).
  • ASC that cannot exclude high-grade squamous intraepithelial lesions (HSIL) (ASC-H).
• Low-grade squamous intraepithelial lesions (LSIL).
• Mild dysplasia.

Minor cervical cell changes found during a Pap test may be caused by:

• Infection (including infection with the human papillomavirus, or HPV).
• Inflammation of cervical cells.
• Natural changes called atrophic vaginitis, caused by menopause.
• Unknown causes.

Minor cervical cell changes may:

• Disappear without treatment, so follow-up Pap tests would be normal.
• Be precancerous and begin to develop into moderate to severe cell changes that eventually may become cancer. Follow-up Pap tests or colposcopy can detect cell changes.

Moderate to severe cell changes

Moderate to severe cervical cell changes (also called moderate to severe dysplasia) mean cell changes that are more likely to be precancerous and develop into cervical cancer if left untreated. Moderate to severe cervical cell changes are classified in the Bethesda system (TBS) as high-grade squamous intraepithelial lesions (HSIL) or atypical glandular cells (AGC). Follow-up evaluation and treatment is needed.

All abnormal Pap tests require follow-up to identify development of more severe cell changes, including cervical cancer. Most abnormal cells can be removed or destroyed before they become cancerous.