PAP Smear

How Are Pap Smear Results Classified?

Laboratories use one of two systems to classify Pap smear results.

Traditional Reporting System

The older system classifies each cell sample as

Class I


Class II


Class III

Mild, moderate, or severe abnormality

Class IV

Carcinoma in situ, that is, a growth that has the characteristics of cancer cells but has not yet reached the deepest layers of the tissue

Class V

Suspicious for an invasive cancer, that is, cancer that is likely to infiltrate and destroy surrounding tissue

The Bethesda System

Developed during a conference of cancer specialists at the National Institutes of Health (NIH), this newer system is replacing the older classification method.

The Bethesda System classifies the adequacy of cell samples as

  • satisfactory
  • limited
  • unsatisfactory

It describes epithelial cells as

  • normal
  • benign or noncancerous
  • abnormal

The Bethesda System further classifies abnormal epithelial cells – the cells that make up the mucous membrane that lines the cervix – as

  • atypical squamous cells of unknown significance (ASCUS)
  • low-grade squamous intraepithelial lesion (LSIL)
  • high-grade squamous intraepithelial lesion (HSIL)

Abnormalities in cells that line the glands of the cervix may be

  • atypical glandular cells of undetermined significance (AGUS)
  • adenocarcinoma, that is, cancer of the glandular cells of the cervix

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