Malignant mediastinal germ cell tumors of various histologies were first described as a clinical entity approximately 50 years ago.
Mediastinal and other extragonadal
germ cell tumors were initially thought to represent isolated
metastases from an inapparent
gonadal primary site.
Etiology
Some investigators suggest that this distribution arises as a consequence of abnormal migration of germ cells during
embryogenesis. Others hypothesize a widespread distribution of germ cells to multiple sites during normal embryogenesis, with these cells conveying genetic information or providing regulatory functions at somatic sites.
Epidemiology
Malignant germ cell tumors of the mediastinum are uncommon, representing only 3 to 10% of tumors originating in the mediastinum. They are much less common than germ cell tumors arising in the
testes, and account for only 1 to 5% of all germ cell
neoplasms.
Clinical Characteristics
Unlike benign germ cell tumors of the mediastinum, malignant mediastinal tumors are usually symptomatic at the time of diagnosis. Most mediastinal malignant tumors are large and cause symptoms by compressing or invading adjacent structures, including the lungs, pleura, pericardium, and chest wall.
Seminomas grow relatively slowly and can become very large before causing symptoms. Tumors 20 to 30 cm in diameter can exist with minimal symptomatology.
Associated Syndromes
Evaluation and Staging
The diagnosis of a...
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