How Does Colon Cancer Develop?

Colon cancer is one of the best-researched cancers in humans. Today it is known that about 90% of intestinal cancers develop from benign intestinal polyps. This degeneration from intestinal polyp (adenoma) to cancer (carcinoma) can take about 10 years. Scientists call this development an adenoma-carcinoma sequence. This is caused by successive genetic changes (mutations) in the mucous membrane cells of the intestinal wall. They eventually lead to the loss of the natural growth control of the cells so that they can spread malignantly and destructively as cancer cells.

Colon cancer is not caused by a single damaging event. It usually takes decades for a critical number of such gene mutations to accumulate in a cell. Over time, i.e. with age, the risk of cancer increases – most cancer patients are therefore older than 50 years. However, genetic changes can also be inherited from parents. Then it takes considerably less time for genetic damage to accumulate, so that cancer can develop here at a younger age. Therefore, special caution is required in the case of a family risk.

Cell division as a weak spot

Gene changes often occur during cell division. Cell division causes the cells in our body to multiply. The human body consists of about 100 trillion cells. In adults, too, body tissue is constantly renewed and new cells are continuously created by cell division. About 50 million body cells die every second – the same number are newly formed every second by cell division!

Before cell division, all genetic information must be duplicated identically so that the genes can be passed on to both daughter cells equally and completely. In order to monitor this important process, nature has created complex control mechanisms that enable the error-free division of a cell into two daughter cells. Scientists now assume that more than 100 genes alone are involved in the monitoring and control of cell division.

Despite sophisticated safety systems, cell division can occasionally lead to damage: During the duplication of genetic information prior to cell division, transmission errors occur. This leads to changes in the genetic material, the so-called mutations. External triggers can also favour such genetic changes. These include environmental influences that promote cancer, such as smoking, solar radiation or chemical substances in food.

Cancer cells grow uncontrolled

Mutations in the genes that regulate and control cell growth are critical. If, over time, a number of such critical gene alterations occur, the affected cell ultimately becomes out of control – it ignores the growth rate of its cell structure, divides more frequently, and all cells derived from it proliferate uncontrollably. A cancerous tumour develops.

Uncontrolled growth is what makes cancer cells so destructive. Doctors and scientists describe cancer cells on the basis of characteristic features:

  • Cancer cells grow uncontrollably and divide unchecked.
  • Under the microscope, their appearance begins to change compared to that of a healthy cell.
  • Cancer cells disregard natural boundaries, they grow into adjacent tissue, they grow invasively.
  • Cancer cells can detach themselves from their cell structure, leave their place of origin and migrate with the blood or lymph to other organs where they form metastases.

Adenoma-carcinoma sequence

In about 90 percent of all cases, colorectal cancer initially develops from benign intestinal polyps. The gene changes responsible for this in the intestinal mucus hatz cell are widely known to scientists today. With each further critical mutation, the cell loses its orderly growth. First a benign tumour develops, later a malignant tumour. The development of healthy intestinal mucosa into intestinal polyps and further into malignant intestinal cancer takes place in several steps:

  1. A single cell of the intestinal mucosa begins to divide uncontrollably due to several critical changes in its genetic material. More and more cells are produced at this site, all of which originate from the same cell.
  2. The cells begin to slide over each other, which can be seen from a small thickening of the intestinal mucosa. This produces a small, benign tumour, a mucous membrane polyp (adenoma).
  3. The permanently dividing cells grow into the interior of the intestine: The intestinal polyp is now clearly visible during a colonoscopy. The polyp still grows benignly, i.e. it does not break through the natural boundaries of the intestinal wall, destroys other wall layers or even adjacent tissue.
  4. After some time, individual cells of the polyp suffer further serious genetic changes: They now ignore the natural boundaries in the tissue; they grow invasively and have become malignant cancer cells (carcinoma). Cancer cells penetrate the entire intestinal wall, detach themselves from their cell structure and are driven by blood and lymphatic fluid to other parts of the body, where they form new cancer colonies (metastases).

The entire development takes time – it is estimated that a small intestinal polyp can develop into intestinal cancer within five to ten years. So there is enough time to detect the intestinal polyp in time and remove it from the body with the help of intestinal cancer screening. Read here how bowel cancer can be effectively prevented.