ABSTRACT
This chapter reviews studies on the concepts of the multistep nature of human colorectal neoplasia and the genetic alterations that may be involved in the tumorigenesis. It discusses in vitro transformation of human and rat colon epithelial cells. In spite of detailed observations by numerous investigators on hundreds of specimens of human colorectal lesions, controversy still exists as to the true origin of the cancer. There have been three major viewpoints, such as the carcinomas originate from hyperplastic polyps, adenomatous polyps, or in situ lesions. Genetic alterations in colorectal neoplasms have been investigated more extensively than any other type of cancer because, in this case, it has been possible to characterize lesions at various stages of their existence which can be obtained in sufficient quantities for the analysis. Several markers have been associated with the development and/or progression of colorectal tumors. Carcinoembryonic antigen (CEA) has been widely used as a clinical marker for colorectal tumors.
