Anterior mediastinal seminoma
Non-specific chest discomfort with clinical signs of superior vena cava compression.
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On PET scan, there is an intensely FDG avid, large mass lesion in the anterior mediastinum. On low dose CT, the lesion is generally homogenous in density with several foci of course calcification. No fat density is seen within the lesion.
The avidity of the large mass is contiguous with a rounded extrapleural lesion at the right lung apex, which may reflect a large supraclavicular lymph node or direct extension from the primary tumor.
The large mass compresses the superior vena cava, resulting in the patient's clinical symptoms and signs.
No additional FDG avid nodal or metastatic disease was identified. In particular, no second hypermetabolic primary lesion was identified in the testes. No pulmonary lesions were demonstrated on review of the lung windows (not shown).
The biopsy of the anterior mediastinal lesion revealed seminoma on pathology. Ultrasound of the testes was normal (and no FDG avid lesions were seen in the testes on PET scan), leading to a diagnosis of primary anterior mediastinal seminoma.
Germ cell tumors are one of the important differential diagnoses for anterior mediastinal masses. Similar to germ cell tumors of the testes and ovaries, the can be divided into seminomatous and non-seminomatous germ cell tumors. In the anterior mediastinum, mature teratoma is the most common histology, however all histological subtypes can be enountered.