Mediastinal germ cell tumor

Malignant mediastinal germ cell tumors of various histologies were first described as a clinical entity approximately 50 years ago.^[when?] 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

• Klinefelter's syndrome
• Hematologic Neoplasia

Evaluation and Staging

The diagnosis of a mediastinal germ cell tumor should be considered in all young males with a mediastinal mass. In addition to physical examination and routine laboratory studies, initial evaluation should include CT of the chest and abdomen, and determination of serum levels of HCG and alpha-fetoprotein.

Treatment

Pure mediastinal seminomas are curable in the large majority of patients, even when metastatic at the time of diagnosis. These tumors are highly sensitive to radiation therapy and to combination chemotherapy. However, the cardiotoxicity of mediastinal radaition is substantial and the standard treatment of mediastinal seminomas is with chemotherapy using bleomycin, etoposide and cisplatin for either three or four 21-day treatment cycles depending on the location of any metastatic disease.

In summary, most patients with mediastinal seminoma can be cured with chemotherapy, and all patients should be approached with this intent. Patients with small tumors (usually asymptomatic) that appear resectable should undergo thoracotomy and attempted complete resection followed by chemotherapy.

The treatment for mediastinal nonseminomatous germ cell tumors should follow guidelines for poor-prognosis testicular cancer. Initial treatment with four courses of bleomycin, etoposide, and cisplatin, followed by surgical resection of any residual disease, is considered standard therapy.

Sources

• Primary Germ Cell Tumors of the Thorax Malignant Mediastinal Germ Cell Tumors
• Knapp RH, Hurt RD, Payne WS, et al. Malignant germ cell tumors of the mediastinum. J Thorac Cardiovasc Surg 1985;89:82-9

References

• Vugrin D, Martini N, Whitmore WF, Goldberg RB. VAB-3 combination chemotherapy in primary mediastinal germ cell tumors. Cancer Treat Rep 1982;66:1405-7.
• Einhorn L, Williams S, Loehrer P, et al. Phase III study of cisplatin dose intensity in advanced germ cell tumors. A Southeastern and Southwest Oncology Group protocol. Proc Am Soc Clin Oncol 1990;9:132.
• Moran CA, Suster S. Primary germ cell tumors of the mediastinum - I. Analysis of 322 cases with special emphasis on teratomatous lesions and a proposal for histopathologic classification and clinical staging. Cancer 1997:80:681-90.

See also

• Mediastinitis
• Mediastinal fibrosis
• Mediastinum