Anal cancer as well as cervical, vaginal, and vulvar cancer can be caused by an infection called human papillomavirus (HPV). Researchers do not know how often anal cancer and dysplasia occur together with cervical, vaginal or vulvar high-grade dysplasia, or invasive squamous cell carcinoma. All of these diseases are caused by the HPV virus and for this reason are thought to be related. Researchers also want to learn how to test for these diseases.