Extraskeletal Ewing's Sarcoma
The Ewing sarcoma family of tumors (ESFT) represents a group of high-grade small round cell tumors, including
Ewing sarcoma of bone, extraskeletal Ewing sarcoma, peripheral primitive neuroectodermal tumor (PNET), and Askin tumor (thoracopulmonary
PNET). Though separately described and thought to be distinct neoplasms, it is now known that these tumors arise from a common
precursor cell, with each entity representing a different expression of the same neoplasm. Distinction is based on cellular
differentiation or anatomic location or both. Ewing sarcoma is poorly differentiated and may arise in bones or soft tissues;
PNET arises in the soft tissues and shows neuroectodermal differentiation.
Each year, up to 400 patients in the United States will be diagnosed
with ESFT. Approximately 80% of cases will occur during the first two decades of life, and 80% of these cases will arise in
the skeleton. In contrast, half or more of primary adult cases are extraskeletal. Patients often present with a painless mass
or vague abdominal or chest pain depending on tumor site. Those with metastatic disease may have fever, malaise, and elevated
markers of inflammation. Spontaneous hemorrhage can lead to rapid growth of a mass or mimic an acutely painful abdomen.
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