ABSTRACT
Anal cancer arises in the anal canal or the perianal area. There are several definitions of the anal canal, but for clinical and practical reasons the definition proposed by Wendell-Smith in 2000 is useful. The anal canal may then be defined as the region extending between two easily recognised and palpable landmarks; the ano-rectal ring and the intersphincteric groove. Different types of malignant tumours can arise in the anal canal and the perianal area. Most tumours are rare, and choice of therapy is dependent on tumour type. Squamous cell carcinoma of the anus, including both tumours of the anal canal and perianal tumours, is the least uncommon malignant disease encountered in this region. Anal cancer accounts for 1%–2% of digestive tract tumours and squamous cell carcinomas of the anus have an annual incidence of 1–2 per 100,000. Anal cancer is more common in women, and abundant data indicates that the incidence is rising.
