Do we know what causes Ewing tumors?
The cause of Ewing tumors is not fully understood, but researchers are learning how certain changes in a cell's DNA can cause the cell to become cancerous. DNA is the chemical in each of our cells that makes up our genes. Genes tell our cells how to function. They are packaged in chromosomes, which are long strands of DNA in each cell. We normally have 23 pairs of chromosomes in each cell (one set of chromosomes comes from each parent). We usually look like our parents because they are the source of our DNA. But DNA affects more than how we look.
Some genes contain instructions for controlling when our cells grow, divide into new cells, and die. Certain genes that help cells grow and divide are called oncogenes. Others that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Cancers can be caused by DNA mutations (changes) that turn on oncogenes or turn off tumor suppressor genes.
Researchers have found chromosome changes that lead to Ewing tumors, but these changes are not inherited. Instead, they develop in children after birth, in a single cell, for no apparent reason.
Nearly all Ewing tumor cells have changes that involve the EWS gene, which is found on chromosome 22. In most cases, the change is a swapping of pieces of DNA (called a translocation) between chromosomes 22 and 11. Less often, the swapping occurs between chromosomes 22 and 21, or rarely between 22 and another chromosome. The translocation moves a certain piece of chromosome 11 (or another chromosome) just next to the EWS gene on chromosome 22, causing the EWS gene to be turned on all the time. The activation of the EWS gene leads to overgrowth of the cells and to the development of this cancer, but the exact way in which this happens is not yet clear.
Lab tests can be used to find chromosomal translocations in Ewing tumor cells (see the section called "How are Ewing tumors diagnosed?"). If doctors are not sure if a tumor belongs to the Ewing family, they can use these tests to confirm the diagnosis.
The gene changes that lead to Ewing tumors are now fairly well understood, but it's still not clear what might cause these changes. It may just be a random event that sometimes happens inside a cell, without having an external cause. There are no known lifestyle-related or environmental causes of Ewing tumors, so it is important to remember that there is nothing these children or their parents could have done to prevent these cancers.
Last Medical Review: 04/24/2012
Last Revised: 01/18/2013