How does cancer in children and teenagers develop?

Author:  Gesche Tallen, MD, PhD, Editor:  Maria Yiallouros, Reviewer:  Prof. Dr. med. Dr. h. c. Günter Henze, English Translation:  Hannah McRae, Last modification: 2012/04/25 https://kinderkrebsinfo.de/doi/e1826

When a child or teenager has been diagnosed with cancer, he or she, as well as the parents, often wonders what they have done to get it, or if they have missed ways to prevent it. In spite of continuous and intensive basic and clinical childhood cancer research during the last decades, it is still unclear what precisely causes cancer in children and teenagers. However, thanks to continuous and successful research we have learned so far:

Healthy cells divide (mitosis). They mature and learn their tasks and functions (differentiation). They age (senescence), and they die (apoptosis/necrosis). These phases of a healthy cell's life are controlled by several mechanisms in the cell and also by signals from other cells. Together, these mechanisms and signals function like a natural inner clock, that determines every cell's life-span.

Cancer develops when the inner clock of a cell gets out of balance. Once a cell has lost its inner clock, the cell cycle is disturbed. As a consequence, cells divide uncontrollably. They do not mature properly, and are thus dysfunctional. They do not age properly and may lack the ability to die.

There are many factors that can cause dysregulations within the cell-cycle, making the development of cancer a complex, multi-step process. In many cases, its origins may lie in changes in the genetic make-up of a cell, such as genes carrying incorrect information (mutations) or chromosomes with missing or extra genes (chromosomal aberrations). These changes to genes and/or chromosomes can result in impaired or lost functions in proteins, that are usually responsible for regulating the cell-cycle, for appropriate signalling from cell to cell and also for the repair of genetic damage.

A hereditary disposition to develop cancer early in life has been described in association with specific (rare) birth defects, that are characterised by certain gene mutations. Nevertheless, cancer is not a hereditary disease.

Children are not little adults. Therefore, childhood cancer differs from cancer in adults in terms of its frequency, type, biological characteristics and its possible causes. While exposure to dietary, lifestyle and environmental factors play a major role in the development of cancers in adults, only a few risk factors, such as ionising radiation and a mother's exposure to X-rays during pregnancy have been identified as risk factors in children. These account for only a small portion of cases.

Childhood cancer researchers have evidence, that the first few cells of various malignancies, such as Wilms tumours, neuroblastomas, germ cells and some brain tumours may already be present at birth. This suggests that changes in certain cells of the body may have already happened in the embryo. However, much more research is needed to completely and accurately describe what causes a specific cancer in a child.

Cancer is not a contagious disease.

So far, there is no scientific evidence that childhood cancer can be caused by human behaviour. Therefore, the current state of knowledge does not allow the conclusion, that you or your child have done anything that may have caused the disease. Although emotional and psychological factors, such as experiences of loss or troubled relationships, are repeatedly being discussed as possible causes, they have not been scientifically proven to be true.