What causes Ewing’s sarcoma?


Produced: May 2018

We aim to provide reliable information about Ewing’s sarcoma. This page contains information of a medical or scientific nature that we have compiled from scientifically reliable sources.

What causes Ewing’s sarcoma?

As the causes of Ewing’s sarcoma are not fully understood, we don’t know how to prevent it from happening.

It has been theorised that it is somehow related to the rapid growth of bones during development and puberty. There are no known inherited risk factors for developing Ewing’s sarcoma i.e. it is not thought to be caused by a faulty gene inherited from a parent.

And there are no specific risk factors for developing Ewing’s sarcoma although it does occur more frequently in Caucasian males. Ewing’s sarcoma is extremely rare in those of African or Asian descent.

Ewing’s sarcoma is characterised by a specific genetic fault, which is described below, but it is unknown what causes the genetic fault.

Humans are made up of around 37 trillion cells. In most cells there is an exact replicate of the DNA, which contains around 20,000 genes. Genes are the set of instructions used by a cell to produce proteins. Each protein is unique and has a specific role to perform, for example, causing a single cell to divide into two cells or as a hormone that determines our mood.

Because DNA is a huge molecule inside our cells, it is packaged into structures called chromosomes. There are 46 chromosomes in most cells – 23 inherited from each parent to make you. The last pair of chromosomes, known as X and Y, are the sex chromosomes. Males have one X and one Y. Females have two X’s.

In 85% of Ewing’s sarcoma patients, a gene on chromosome 22 called EWSR1 breaks off and joins another gene on chromosome 11 called FLI1 (see Figure 1 below).

Individually, EWSR1 and FLI1 are normal genes that we need for our cells to function properly. However, when fused together as EWSR1-FLI1 they cause cells to rapidly divide and form tumours. Detection of EWSR1-FLI1 in tumour specimens helps doctors to diagnose Ewing’s sarcoma.

EWSR1 can break off and fuse with other genes on other chromosomes causing Ewing’s sarcoma, but these are much rarer.

Figure 1 (Diagram showing pairs of chromosomes in a human cell)

Diagram showing pairs of chromosomes in a human cellProduced: March 2018

Published: December 2018

Review: December 2021

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