Primary Seminoma Arising in the Superior Vena Cava.

A 43-year-old man presented with a 1-month history of progressive facial and neck swelling without an identifiable trigger. He was diagnosed with superior vena cava syndrome (SVCS). A further chest CT showed an irregular low-density mass within the superior vena cava (SVC), and 18 F-FDG PET/CT showed significant tracer uptake. Malignancy was suspected. Among the tumor markers tested, only NSE was mildly elevated (33.4 ng/mL, normal range, <7 ng/mL). Subsequently, the patient underwent resection of the SVC mass combined with SVC replacement; the final pathologic diagnosis was classic seminoma.