What it is & what causes it?

What is Ewing’s sarcoma?

Ewing’s sarcoma is a type of primary bone cancer. Primary bone cancers are tumours that start in the bone, rather than cancer that has spread to the bone from somewhere else in the body. Ewing’s sarcoma is usually diagnosed in children and adolescents and it is very rare with fewer than 100 cases diagnosed each year in the UK.

Most Ewing’s sarcomas arise within the legs and pelvis. However, it can arise in other bones such as those in the arms, shoulder blades, spine, ribs and collarbone. Less commonly, Ewing’s sarcoma can form in the soft tissues that support and protect the body’s organs (soft tissue Ewing’s sarcoma).

The most common symptoms of Ewing’s sarcoma are pain and swelling at the tumour site. These symptoms are often attributed to other causes such as injuries. A distinctive feature of Ewing’s sarcoma is that the pain can be worse at night. The pain may be so bad that it is difficult to fall asleep. Less frequently, symptoms can include fever, weight loss and tiredness.

a type of primary bone cancer

Primary bone cancers are tumours that start in the bone.

Mostly within the legs & pelvis

Other areas include arms, shoulder blades, spine, ribs and collarbone.

Symptoms include pain & swelling

Distinctively, the pain can be worse at night.

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; it 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. This diagram shows pairs of chromosomes in a human cell).

What causes Ewing’s sarcoma?

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.