Extraskeletal Ewing's Sarcoma Masquerading as Infantile Benign Neck Mass.

Despite being the second most common malignant bone tumor, Ewing's sarcoma remains uncommon in younger children and seldom seen in neonates and infants. Extraskeletal locations are even rarer, hardly ever suspected, and often misdiagnosed, causing delays in management. The histologic similarities of Ewing's sarcoma to more common pediatric small-blue-round-cell tumors such as lymphoma and neuroblastoma necessitate immunohistochemistry and molecular genetics for clinching the diagnosis. We report a soft-tissue Ewing's sarcoma in a 4-month-old female infant masquerading as a benign neck mass clinically, radiologically, cytologically, and intraoperatively. We also reviewed literature for any existing guidelines on when to biopsy neck masses in the pediatric population.