Retroperitoneal Ewing's Sarcoma in a Woman with Advanced Breast Cancer Delineated by Contrast-Enhanced Ultrasound: A Case Report

Extraosseous Ewing's sarcoma is a malignant mesenchymal tumor much rarer than skeletal Ewing's sarcoma. The synchronous or metachronous occurrence of advanced breast cancer with retroperitoneal Ewing's sarcoma is extremely rare. To date, only a few cases of extraosseous Ewing's sarcoma with contrast-enhanced ultrasound findings have been reported. This study aims to report a case of a retroperitoneal Ewing's sarcoma in a 39-year-old woman with advanced breast cancer, where grayscale ultrasound, contrast-enhanced ultrasound, and computed tomography findings were included. To our knowledge, this is the first reported case of ultrasound and contrast-enhanced ultrasonography manifestation of retroperitoneal Ewing's sarcoma as a second primary tumor.