Imaging Characteristics of Periosteal Ewing Sarcoma: A Rare Case Report and the Diagnostic Challenges in Differentiating Surface-Based Bone Lesions

Abstract

Ewing’s sarcoma (ES) is a malignant small round-cell tumor that typically develops within the medullary cavity of bone. A rare variant, known as periosteal Ewing’s sarcoma (PES), arises from multipotent mesenchymal cells located in the periosteum. This subtype predominantly occurs in males, with the highest incidence during the second decade of life, and most commonly affects the femur. Due to its non-specific clinical and radiological features, PES can be misdiagnosed as other surface-based bone lesions. We report a case of a 7-year-old boy who was admitted with progressively worsening right thigh pain over a two-month period. Radiographic, computed tomography (CT), and magnetic resonance imaging (MRI) revealed a destructive cortical lesion of the femur, initially suggestive of periosteal osteosarcoma (POS). The patient subsequently underwent an ultrasound-guided biopsy. Histopathological examination, combined with immunohistochemical analysis, confirmed the diagnosis of periosteal Ewing’s sarcoma. This case highlights the diagnostic challenges associated with periosteal Ewing’s sarcoma and underscores the importance of recognizing its imaging characteristics—particularly in differentiating it from other surface-based bone tumors—within the appropriate clinical context.