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A 23-year-old woman has a low-grade squamous intraepithelial lesion on her Papanicolaou (Pap) test. One colposcopic view of her cervix shows acetowhite changes consistent with a cervical intraepithelial neoplasia grade 1 lesion (CIN 1) (Figure 91-1). She has no other suspicious findings and biopsy of the acetowhite area confirms CIN 1. The endocervical sampling is negative for neoplastic disease. During the follow-up visit, the doctor and patient together decide to proceed with watchful waiting and repeat Pap and human papillomavirus (HPV) co-testing at 12 and 24 months.


Colposcopic view of acetowhite changes on the cervix of cervical intraepithelial neoplasia grade 1 lesions after the application of acetic acid. Note the irregular geographic borders. (Reproduced with permission from E.J. Mayeaux, Jr., MD.)


Our knowledge of the genesis and development of cervical cancer has grown greatly over the last 30 years. It was once believed that HPV infection and CIN 1 disease were the first steps in cancer formation. We now know that HPV infection and CIN 1 are essentially the same thing and will resolve without treatment in most immunocompetent women. Which women will progress to high-grade dysplasia or cancer is not completely understood.


  • In low-grade squamous intraepithelial lesion (LSIL) Pap tests, the abnormalities are typically associated with HPV infection and are histologically called CIN grade 1 lesions.1 Overall rates of Pap test abnormalities are often estimated from regional studies. For example, in an observational cohort study of routine cervical tests in the northwestern United States, in women of all ages (n = 150,052), atypical squamous cells was diagnosed at a rate of 9.8 per 1000, LSIL was diagnosed at a rate of 3.5 per 1000, and negative routine tests occurred at a rate of 278.5 per 1000.2

  • In HPV vaccine age groups, there have been significant reductions in the CIN incidence per 100,000 women screened for all grades of CIN. In female individuals 15 to 19 years old, the incidence of CIN 1 dropped from 3468.3 to 1590.6 per 100,000, for CIN 2 from 896.4 to 414.9, and for CIN 3 from 240.2 to 0 per 100,000.3


  • Essentially all CIN is caused by HPV. Ten percent to 15% of CIN 1 lesions will also develop CIN 2-3, and 0.3% will eventually develop cervical cancer.4

  • There is no way to determine which CIN 1 lesions (Figures 91-1, 91-2, 91-3) or simple HPV lesions (Figures 91-4 and 91-5) will develop high-grade disease.

  • Colposcopy is the standard of care for assessing abnormal cervical cancer screening tests and cervical dysplasia. It entails the use of a field microscope to examine the cervix after acetic acid (see ...

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