Development of Colorectal Cancer

Colon Cancer and Rectal Cancer

A tumor which is located in the upper portion of the large bowel is defined as colon cancer; a tumor located in the last portion of the large bowel, in the region between the rectum and anal sphincter, is defined as rectal cancer.

“Colorectal carcinoma” combines both types of cancer.

Genetic Alterations
According to the current standard of knowledge, cancer always develops from alterations in the genetic information program of single cells. These so-called gene mutations mostly arise during cell division. Usually the process of cell division is regulated by complex control mechanisms of the organism. In case these control mechanisms fail, or if the altered cell fails to die as a result of these control mechanisms, such altered cells can continue to divide and pass their new characteristics on to their daughter cells. These cells multiply, forming a small thickened area (hyperplasia) on the intestinal mucosa. The area tends to either grow into a little stalk (pedunculated) or lie rather flat on the wall of the colon (sessile) directly on the mucosa. Such a small thickened area (called a polyp or adenoma) usually is benign and can be detected and removed during a colonoscopy. A big part of these polyps remains benign, but some of these benign polyps potentially turn into a malignant tumor (a so called carcinoma). This conversion occurs over a longer period of time and in several steps, involving additional genetic cell alterations: The tumors, still benign in their early stage, circumvent growth control mechanisms of the organism and begin to proliferate and invade into the natural boundaries of the colon wall. They disassociate from their normal cellular surroundings, invading and destroying adjacent tissues, and possibly reach other compartments of the body via blood and lymph liquid, developing new tumors, termed metastases.