Ewings Family Tumors
Ewings sarcoma is a cancer that was first described by James Ewing in 1921 as a "diffuse endothelioma of bone". Dr. Ewing noted that although the sarcoma was highly aggressive, that it was highly sensitive to radiation therapy.
Since the original description by Dr. Ewing, a number of theories concerning what cell type gives rise to Ewings sarcomas have been developed. A variety of studies have pointed toward the tumor cells arising from a primitive cell in nervous tissue. A similar malignancy that arises in soft tissues outside of the brain, but thought to be similar to primitive brain tumors is called the primitive neuroectodermal tumor (PNET).
PNET's and Ewings sarcomas were found to have a common change (a chromosomal translocation) in the DNA structure. Thus, these tumors were grouped into a class of cancers entitled Ewings Family of Tumor (EFT), which also includes neuroepithelioma, atypical ES, and Askin tumor (ES of the chest wall), all of which demonstrate a particular chromosomal translocation involving chromosomes 11 and 22. The gene from chromosome 22 encodes a Ewings sarcoma gene (EWS) and is a gene that is involved in the regulating activity of other genes. A gene from chromosome 11, which is called FLI1, is also involved in regulating other genes. The translocation results in a fusing of theses 2 genes into a new fused gene that encodes an altered protein. The product of the gene fusion regulates other genes in an abnormal fashion that promotes cancerous growth.