Askin Tumor in an Adult: Recognizing a Rare Chest Wall Presentation of Ewing Sarcoma.

Ewing's sarcoma (ES) is an uncommon and aggressive bone tumor most commonly seen in children and adolescents. Chest wall involvement in adults is particularly rare. We report a 39-year-old woman with chest wall ES. She presented to the emergency department with unrelated symptoms, including flank pain and fever. A chest wall mass was incidentally identified on abdominal CT. Initial imaging had shown a well-circumscribed lesion that resembled a benign entity such as a lipoma or inclusion cyst, but over time, it progressively enlarged. Diagnosis was confirmed by imaging, histopathology, and molecular testing. Management included broad surgical excision and chemotherapy. Chest wall ES in adults is an atypical occurrence that may initially resemble benign diseases. This case highlights the importance of maintaining a broad differential diagnosis, especially for incidental or indolent-appearing soft tissue lesions, and demonstrates the diagnostic value of correlating evolving imaging findings with clinical judgment over time.