38 year old previously healthy man presented to the ER with new onset of dyspnea and chest pain.
B-HCG and alphafetoprotein are within normal limits
Chest X-ray shows a large anterior mediastinal mass. Contrast enhanced thoracic CT shows a mildly heterogeneous (central low density) lobular anterior mediastinal mass with mild mass effect on the subjacent vasculature, no evidence of direct invasion of nearby structures, and little enhancement.
• Germ cell neoplasm
• Thymic carcinoid/carcinoma
• Metastasis from unknown primary (Renal, testicular, head and neck, melanoma)
Dx: Malignant Germ Cell Tumor (mixed)
Dx Confirmed by: Biopsy histology including isochrome 12p staining.
Isochrome 12p is a histologic genetic stain that is specific for germ cell neoplasms.
The anterior mediastinum can harbor primary germ cell neoplasms as well as germ cell metastases from primary testicular tumors. This patient had a subsequent scrotal ultrasound (images not available) showing coarse testicular calcifications. This could be a serendipitous finding or represent a “burnt–out” testicular neoplasm.
PET CT evaluation of the patient showed abnormal FDG activity only in the mediastinum. For now, this case is being approached as a primary mediastinal mixed germ cell tumor.
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