Cancers arising distal to the dentate line have a squamous cell histology, ulcerate more frequently, and represent approximately 55 percent of anal tumors. The prognoses for patients with cuboidal and squamous cell cancers of the anus are identical when corrected for tumor size and the presence or absence of nodal involvement.
Anal cancers occur most frequently in individuals with a history of chronic anal irritation.
In the general population, anal cancers arise most commonly in middle-aged individuals, develop more often in women than in men, and are most commonly associated with bleeding, pain, the sensation of a perianal mass, and perianal pruritus at the time of diagnosis. Tumor recurrences have been reported in approximately 20 percent of these patients. It appears, therefore, that about 70 percent of patients with anal cancers can be cured with nonoperative treatment and that disfiguring surgery should be reserved for that minority of patients who are found to have residual tumors after being managed initially with radiation therapy combined with chemotherapy.