Primary Ewing Sarcoma of Seminal Vesicle on PET/CT

Ewing sarcoma is an aggressive malignancy that most often presents as an undifferentiated primary bone tumor; less commonly, it arises in extraosseous soft tissues of mesenchymal cell origin. Primary extraosseous involvement of seminal vesicle is rarely reported. Herein, we describe FDG PET/CT and MRI findings of a 55-year-old man who presented with a pelvic mass, which was confirmed to be primary Ewing sarcoma/primitive neuroectodermal tumor arising from seminal vesicle by histopathologic findings.