What is Ewings Sarcoma (PPNET)

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By Chris Ryan and Dr. Mahesh Kanojia

Endothelial Myeloma or popularly known as the Ewing’s sarcoma (also Ewing’s tumor) is the name given to a set of malignant cell sarcomas which are usually small and which affect the bones. They are also known as EFT or Ewing’s family of tumors. This particular cancer occurs usually in long bones within the marrow of the midshaft and the commonly affected bones are the shinbone, thighbone or the upper arm. This rare form of cancer is frequently seen in young children and young adults (less than 20 years). Its occurrence is found to be twice as much in boys than girls.

PPNET (peripheral primitive neuroectodermal – or neuroepithelial – tumor) is a bone and soft tissue related tumor to which Ewing’s sarcoma is closely associated. A specific abnormality of chromosomes is shared by both tumors (chromosomes 11 and 22 having a translocation). While they share many similar characteristics, PPNET can be differentiated a lot easier and frequently exhibits neuroendocrine features (i.e. the production of hormones and potent biological substances). This is absent in a proper case of Ewing’s sarcoma. Besides the chromosomal abnormality they share, both tumor types are treated with chemotherapy because their response to it is very similar.

Ewing’s primarily affects the femur or thighbone. Annually about 1/4th of all ES cases in America account for tumors in this specific bone. The pelvis is another very common (2nd most common) site to which about 25 percent can be attributed. Ewing’s can also occur in the bones of the foot along with the tibia and fibula. Also, in about 16 percent of cases an upper extremity is usually affected. The rest are in general found in places like the ribs, clavicle, vertebrae, skull  and the jaw.

Adults above 20 years of age rarely develop Ewing’s, but it has been known to happen. In such instances the treatment process for adult patients is exactly like the children. Children are able to cope with chemotherapy a bit better than adults; however there is always the possibility of long-term damage stemming from the treatment (primarily radiation) which may lead to retardation in bone growth. 

Its unique appearance allows Ewing’s sarcoma to be be easily recognized under the microscope. There are masses of small round cells which are blue in color in the tumor and these are an indicator of this particular cancer. These cells contain glycogen along with the MIC2 gene product which can also be detected in the tumor.

In osteosarcoma, the patient will not necessarily feel pain till the disease is quite advanced. However in Ewing’s, pain is evidenced very early because of the local pain the patient suffers.


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