Anal margin or perianal skin is arbitrarily defined as a skin tissue with a radius of 5 cm from the anal verge, consisting of keratinizing squamous epithelial tissue containing hair follicles. A radius of 5 cm approximately equates to a circle of area of 78.5 cm2 centered on the anal verge.
- 1. Surabhi VR, Menias CO, Amer AM, Elshikh M, Katabathina VS, Hara AK, Baughman WC, Kielar A, Elsayes KM, Siegel CL. Tumors and Tumorlike Conditions of the Anal Canal and Perianal Region: MR Imaging Findings. Radiographics : a review publication of the Radiological Society of North America, Inc. 36 (5): 1339-53. doi:10.1148/rg.2016150209 - Pubmed