Bilateral Testicular Mass Presenting as a Rare Manifestation of Extramedullary Plasmacytoma on 18F-FDG PET/CT.

We present the case of a 48-year-old man diagnosed with metastatic Ewing sarcoma who was referred for 18F-FDG PET/CT for treatment response evaluation following chemoradiotherapy. The patient also had complaints of new-onset testicular swelling at the time of imaging. Although the metastatic bone disease showed a complete metabolic response to treatment, 18F-FDG PET/CT demonstrated significantly increased metabolic activity in bilateral testicular mass. Consequently, the patient underwent bilateral orchiectomy, and histopathologic examination revealed bilateral testicular plasmacytoma, a rare manifestation of extramedullary plasmacytoma.