Primary tumors less than two centimeters in size, and well-differentiated tumors, respond better to treatment. Cancer of the anus begins its growth in the surface layer of the skin, called the epithelium. These pre-cancerous cells are relatively harmless until they develop into cancer. According to the American Cancer Society, about 1,400 cases of anal cancer are expected in American men this year. About 200 of these men will die of the disease.
Anal cancer is often mistaken for hemorrhoids, doctors say.
Other symptoms include pain, itching, discharge and swelling. Some experience no symptoms at all.