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.
â€˘ Germ cell neoplasm
â€˘ Thymic carcinoid/carcinoma
â€˘ 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 â€śburntâ€“outâ€ť 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.
Nonseminomatous malignant germ cell tumors can derive from embryonic, extraembryonic (Yolk sac, Choriocarcinoma), or a combination of tissues (mixed germ cell). These tumors typically present as large heterogeneous soft-tissue mass that invades surrounding structures. They oftentimes have central hemorrhage or necrosis. The margins are well circumscribed but irregular with contrast enhancement of the tumor periphery. Invasion of mediastinal structures is extremely common (see SVC syndrome below). Often they are accompanied by pleural or pericardial effusions.
The peak occurrence is age 20-40 predominantly in males (M:F = 9:1). When these tumors occur in children they are equally distributed among males/females. They are associated with Klinefelter syndrome (47 XXY chromosomal abnormality) in 20% of patients. In Klinefelter syndrome, they are typically found in young boys with precocious puberty.
Presenting symptoms include chest pain, dyspnea, cough, weight loss, and fever. In 90%+ of patients there are symptoms of superior vena cava syndrome. Laboratory analysis typically demonstrates elevated serum levels of LDH (60%), hCG (30%), and alpha-fetoprotein (80%).
Treatment is based on cisplatin-based chemotherapy and tumor resection when possible with a long-term survival approaching 50%.
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