How does cancer develop

How cancer develops


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The development of cancer is a complex process. Years can pass between the development of the individual cancer cell and the occurrence of a detectable cancer.

The starting point is the genes

The starting point of cancer is the genome. Damage occurs in the genes, the carriers of the genetic make-up, which can no longer be repaired. Three groups of genes play a role: the oncogenes, the tumor suppressor genes and the repair genes. All three are also found in healthy cells, where they regulate the growth and differentiation (“maturation”) of the cells. Oncogenes promote cell growth; tumor suppressor genes suppress it. If changes, so-called mutations, occur in these genes, the body's repair system intervenes and repairs the damage. In most cases this happens without any problems.

Sometimes, however, the repair system fails. An imbalance then arises between oncogenes and tumor suppressor genes, which leads to uncontrolled growth of cells.

The genetic changes that lead to cancer occur in most cases spontaneously in the course of life. The tendency to develop cancer is more rarely inherited. The triggers of the spontaneous gene changes can at least partially be traced. Cigarette smoking, heavy alcohol consumption, excessive exposure to sunlight or infections with some pathogens such as the human papillomavirus (HPV) are known cancer-causing factors. The cause of the triggering of cancer is a change in the genetic make-up or the regulation of the corresponding genes.

Cancer: Often grows in secret for a long time

The reasons why the body's repair system fails can be many. Cancer cells have ingenious ways of making themselves "invisible": They can, for example, camouflage themselves by adopting the typical characteristics of healthy cells or the properties of other tissues. The programs in cancer cells that are responsible for the normal aging process and cell death can also fail. In this case, the cancer cells become immortal, so to speak.

Some cancers develop very quickly and aggressively. Sometimes, however, cancer cells also grow in secret for a long time. Years, sometimes even decades, can pass between the development of a single cancer cell and the occurrence of a detectable cancer.

Metastases: The tumor spreads

In contrast to benign tumors, malignant tumors tend to spread beyond their place of origin into the body. In doing so, they overcome the limits of the tissue layer in which they were created and gradually grow into the surrounding tissue. In addition, many types of cancer use the lymphatic and blood vessel system, reach other organs through it and settle there daughter tumors, so-called metastases.

When and in which organs the tumors metastasize largely depends on the type of tumor and the origin of the disease.

Differentiation between benign and malignant tumors

Whether a tumor is benign or malignant influences the expected course of the disease and the choice of therapy. Benign tumors can become very large, but usually do not grow beyond the limits of their original layer. Therefore, they do not form metastases.

Malignant tumors, on the other hand, send out long-fingered cell extensions at an early stage, which can overcome the organ boundaries and continue to grow inexorably. They penetrate the lymphatic or blood vessels just as early and spread throughout the body. Sometimes this happens at a stage when the cancer has not yet been diagnosed.

Features of benign tumors

  • slow growth
  • sharp delimitation
  • no blood vessel ingrowth
  • do not grow into the environment
  • do not form daughter tumors (metastases)
  • under the microscope "mature" cells can be seen.


Features of malignant tumors

  • rapid growth
  • blurred boundary
  • penetrate blood vessels and "use" them to spread
  • unlimited, uninhibited "proliferation", whereby the surrounding tissue is destroyed
  • strong tendency to relapse after initially successful therapy
  • can form daughter tumors (metastases)
  • indistinct, "immature" cells can be seen under the microscope.



Last content update on: April 10th, 2017

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Last accessed on: May 21, 2021 10:57 p.m.