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Ewing's sarcoma site here
Ewing's sarcoma is a highly malignant tumor that is
a type of peripheral primitive neuroectodermal tumor (PNET). Ewing's sarcoma
is found in the lower extremity more than the upper extremity, but any
long tubular bone may be affected. The most common sites are the metaphysis
and diaphysis of the femur followed by the tibia and humerus. Ewing's
sarcoma is most common in the first and second decade but may affect persons
from age 2 to 80. This tumor preferentially affects whites
more than blacks and Asians. The ratio of male to female is 3:2.
The clinical presentation of Ewing's sarcoma includes
pain and swelling of weeks or months duration. Erythema and warmth of
the local area are sometimes seen. Osteomyelitis is often the initial
diagnosis based on intermittent fevers, leukocytosis, anemia and an increased
Radiologically, Ewing's sarcoma is often associated
with a lamellated or "onion skin" periosteal reaction. This
appearance is caused by and splitting and thickening of the cortex by
tumor cells. The lesion is usually lytic and central. Endosteal scalloping
is often present. The "onion-skin" appearance is often followed
with a "moth-eaten" or mottled appearance and extension into
soft tissue. . Bone marrow infiltration is not obvious on plain x-ray.
While Ewing's sarcoma is usually lytic it may present as a sclerotic lesion
with bone expansion. CT is helpful in defining bone destruction. MRI is
essential to elucidate the soft tissue involvement because with TI-weighted
images the tumor has low intensity compared to the normal high intensity
of bone marrow. On :1 2 -weighted images the tumor is hyper intense compared
to muscle. Ewing's sarcoma has increased uptake on bone scan.
Grossly, the tumor is gray to white in color and poorly
demarcated. The consistency is soft and gray and sometimes semi-liquid
especially after breaking through the cortex. Areas of hemorrhage and
necrosis are common. The destruction is often greater on gross appearance
than was visible on
radiographs.Under the microscope, Ewing's sarcoma consists of densely
packed uniform small cells in sheets. The cells have scant cytoplasm without
distinct borders. The cells are two to three times as big as lymphocytes
and have a single oval or round nucleus without prominent nucleoli. The
tumor spreads through Haversian canals which cause the appearance of permeative
margins on x-ray. Glycogen is present within the cells causing a positive
reaction to periodic acid-schiff (PAS) stain. Most Ewing's sarcomas are
positive with HBA-71 or 0-13 stain which is an antibody to the protein
product of myc 2. The microscopic differential includes lymphoma and metastatic
neuroblastoma which must be excluded by reticulin stain and urine vanillyl
mandelic acid and homovanillic acid respectively. Rhabdomyosarcoma is
ruled out if the specimen stains negatively with desmin, myoglobin and
actin stains.A neural origin is supported by electron microscope findings
of pseudorosettes. This is further supported by the common finding in
Ewing's sarcoma and primitive neuroectodermal tumors of choline acetyltransferase
and the translocation t(11:22)(q24;ql2). It is thought that Ewing's sarcoma
with its few organelles is the poorly differentiated end of the spectrum
of PNET. Neuroepithelioma is an example of well differentiated PNET and
has neurosecretory granules and neuritic processes.
Treatment for Ewing's sarcoma includes surgery, radiation
and multi-drug chemotherapy. Radiation or chemotherapy with vincristine,
dactinomycin and cyclophophamide (VAC) are used preoperatively. Adjuvant
chemotherapy follows surgery and decreases recurrences.i The tumor metastasizes
to lungs and lymph nodes. Poor prognostic signs include increased age,
increased ESR and leukocytosis at presentation.
Eggli, KD et al., Ewing's Sarcoma, Radiologic Clinics of North America,
31(2):325-337, March, 1994.
Bulloughs, Peter, Orthopaedic Pathologv (third edition), Times Mirror
International Publishers Limited, London, 1997.
Fletcher, Christopher, Diagnostic Histopathology of Tumors, Churchill
Livingstone:New York, 1990.
Huvos, Andrew, Bone Tumors:Diagnosis Treatment and Prognosis, W.B.Saunders,