Ewing's Sarcoma

 

There are some characteristics for Ewing’s Sarcoma that will help us in remembering this malignant bone tumor. Ewing’s Sarcoma occurs more in males between the ages of 5-30 years old. Ewing’s Sarcoma occurs in the diaphysis of bone about 50% of the time. It occurs

mostly in the femur, the tibia, the pelvis and also in the spine. The shaft of the fibula is a special place for Ewing’s Sarcoma. X-ray will show a “moth eaten” appearance. The tumor is permeative. The tumor has an “onion skin” or “sunburst” appearance on x-ray due to periosteal reaction. The x-rays may show Codman triangles when the tumor breaks into the cortex and the newly formed reactive bone formation in an attempt to infiltrate outside the bone, invading the soft tissue. MRI will show infiltration of the marrow and a large soft tissue component. The tumor will have small, round, blue cells. The nuclei are prominent and there is minimal cytoplasm. The cells may arrange in a pseudorosette fashion.

Genetics

11;22 translocation

Leads to the formation of a fusion protein EWS/ FLI-1
Ewing’s Sarcoma mimics infection. The patient will complain of pain, fever, tenderness, or a mass or swelling. Sedimentation rate could be high. The white blood cell (WBC) count could be high. You need to do a bone marrow biopsy to rule out metastasis to the marrow. The tumor is negative for cytokeratin test and reticulin test, which tests for lymphoma.

 

Immunostaining:

CD99 + MIC2 + Vimentin + Periodic acid- Schiff (PAS) = Contains Glycogen

 

Treatment of Ewing’s Sarcoma

All malignant bone tumors will be treated with wide resection, regardless if it is a high grade or a low grade malignant tumor. When it is a high grade malignant tumor, you will add chemotherapy to the wide resection. Ewing’s Sarcoma in particular can also respond to radiation therapy. In brief, the treatment protocol for Ewing’s Sarcoma is chemotherapy and local control of the tumor, either by wide resection, by radiation therapy, or by both. You will use the chemotherapy before the wide resection. The surgical resection can be used when the lesion can be removed with wide margins. The radiation therapy treatment has problems of its own, but it is used for local control of the tumor in areas where limb salvage is not possible (e.g. pelvis). Radiation is also used if the patient has a positive post-resection margin or in case of advanced disease with metastatic lesions. Radiation can also be used in surgically inaccessible sites or when there is a poor chemotherapy response.

Author
Nabil Ebraheim, MD

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