Cancer of the anal canal

Anal neoplasms are uncommon lesions, representing only 1-4% of all malignant tumors of the lower gastrointestinal tract. There exists a broad spectrum of malignant potential within this group of tumors. Benign lesions range from easily treated in situ Bowen’s disease to locally aggressive verrucous lesions. Among malignant neoplasms, prognosis varies from early-stage squamous cell carcinoma, which generally responds favorably to treatment, to anal adenocarcinoma and malignant melanoma, which are rarely associated with long-term survival. In keeping with this diversity, favored treatment for each of these lesions is highly variable, and determined principally by histological subtype, location relative to the anal canal and margin, size, depth of penetration, the presence of metastases, and increasingly, the presence of any comorbidities, particularly AIDS.