Anal cancer and intraepithelial neoplasia screening: A review

Abstract

This review focuses on the early diagnosis of anal cancer and its precursor lesions through routine screening. A number of risk-stratification strategies as well as screening techniques have been suggested, and currently little consensus exists among national societies. Much of the current clinical rationale for the prevention of anal cancer derives from the similar tumor biology of cervical cancer and the successful use of routine screening to identify cervical cancer and its precursors early in the disease process. It is thought that such a strategy of identifying early anal intraepithelial neoplasia will reduce the incidence of invasive anal cancer. The low prevalence of anal cancer in the general population prevents the use of routine screening. However, routine screening of selected populations has been shown to be a more promising strategy. Potential screening modalities include digital anorectal exam, anal Papanicolaou testing, human papilloma virus co-testing, and high-resolution anoscopy. Additional research associating high-grade dysplasia treatment with anal cancer prevention as well as direct comparisons of screening regimens is necessary to develop further anal cancer screening recommendations.

Keywords: Anal Papanicolaou test; Anal cancer; High-resolution anoscopy; Screening; Secondary prevention.

Figure 1

San Francisco algorithm for anal cancer screening of high-risk patients. ASC-US: Atypical squamous cells of undetermined significance; LSIL: Low-grade squamous intraepithelial lesions; HSIL: High-grade squamous intraepithelial lesions; Pap: Papanicolaou; HRA: High-resolution anoscopy; AIN: Anal intraepithelial neoplasia (adopted from Chin Hong, Palefsky. Clin Inf Dis 2002).

Figure 2

Johns Hopkins Hospital algorithm for anal cancer screening of high-risk patients. Pap: Papanicolaou; HRA: High-resolution anoscopy; ASC-H: Atypical squamous cells of undetermined significance, cannot rule-out high-grade dysplasia; AIN I: Anal intraepithelial neoplasia I; PCP: Primary care physician; LSIL: Low-grade squamous intraepithelial lesion; AIN II: Anal intraepithelial neoplasia II; AIN III: Anal intraepithelial neoplasia III.