 SCCA appears to have many similarities to cervical cancers. HPV has been detected in 88 of anal cancer specimens with HPV-16 found in 73 of SCCA and HPV-18 in 7 1. In addition, SCCA develops in the transformation zone between the squamous epithelium of the anus and the columnar epithelium of the rectum, is frequently associated with dysplasia of the anus and may be preceded by squamous intraepithelial changes which are also associated with HPV. 