College of American Pathologists
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  Categorizing anal-rectal cytology challenges





cap today



September 2006
PAP/NGC Programs Review

Christine Noga Booth, MD

Anal-rectal cytology, or ARC, is used as a screening and diagnostic test to detect human papillomavirus-related squamous cell carcinoma and its precursors in the anogenital canal of patients at risk. A comprehensive review of ARC, from obtaining specimens to treating the patient, was published in the May 2004 issue of CAP TODAY.1

Like gynecologic specimens, adequate ARC specimens contain squamous epithelium, a transition zone of squamous metaplastic cells, and glandular epithelial cells from the rectal mucosa. Within a clinical setting, it is recommended that modified Bethesda terminology be used to report the results on these specimens.2

In 2005, ARC specimens were introduced as challenges in the Interlaboratory Comparison Program in Nongynecologic Cytopathology. For the purposes of the nongyn program, and contrary to how we are to practice in a clinical setting, any ARC challenge interpreted as a low-grade squamous intraepithelial lesion (LSIL), high-grade squamous intraepithelial lesion (HSIL), squamous cell carcinoma, or other malignant neoplasm should be categorized by participants as “positive for malignancy” on the results form. Though this may appear to be an overcall for LSIL and HSIL, the form itself cannot be changed because other nongyn cases are reported on the same form.

Future results forms for the Interlaboratory Comparison Program in Nongynecologic Cytopathology will contain a footnote to emphasize this and help participants score these cases correctly. Internally, this is being done for record-keeping purposes within the CAP’s data collection system.


  1. Darragh TM, Winkler B. The ABCs of anal-rectal cytology. CAP TODAY. May 2004:42–50.
  2. Darragh T, Birdsong G, Luff, R, Davey D. In: Solomon D, Nayar R, eds. The Bethesda System for Reporting Cervical Cytology: Definitions, Criteria, and Explanatory Notes. 2nd ed. New York: Springer-Verlag; 2004.

Dr. Booth, a member of the CAP Cytopathology Committee, is in the Department of Anatomic Pathology, Cleveland Clinic Foundation.