Abstract: |
Colorectal and anal cancers, with more than 150 000 new cases annually in the United States alone, are the fourth most common malignancy and the second leading cause of cancer-related death in the United States.1 In one population-based study in the United States, adenocarcinoma accounted for 97% of all large bowel cancers, with the remaining 3% being cancers of histologic varieties other than adenocarcinoma (see Table 1).2 Of these 3%, about one-half were anal carcinomas (squamous and cloacogenic) and one-third were carcinoid, or neuroendocrine tumors. The rest were tumors rare to the large intestine, such as lymphoma, sarcoma, and melanoma. These nonadenocarcinoma tumors of the colorectal and anal region have distinctive epidemiologies, clinical traits, and pathologies. Treatment and prognoses of these tumors vary greatly, and will be discussed in this chapter. © 2006 John Wiley & Sons, Ltd. |