Technique of Mediastinal Germ Cell Tumor Resection

Abstract

The anterior mediastinum represents the second most common site of germ cell tumor origin. Nonseminomatous germ cell cancers not only comprise the main category of the malignant germ cell tumors arising in the mediastinum (PMNSGCT) but also the most challenging from both oncologic and surgical standpoints. Although histologically similar to their more commonly occurring testicular counterparts, PMNSGCT have an overall worse prognosis and therefore have been categorized as “poor risk” along with other subsets of testicular nonseminomatous germ cell tumors. The majority of PMNSGCTs occur in males 20 to 40 years of age. Most patients present symptomatic secondary to a rapidly growing anterior mediastinal mass. Computed tomographic (CT) scans typically demonstrate a large heterogeneous mass. Local invasion into lung, great vein, and pericardium is common and even direct cardiac chamber/proximal great artery involvement can occasionally be present. Associated pericardial and pleural effusions are also common but typically not malignant in nature. For any young adult male presenting with a mass in the anterior mediastinal compartment, obtaining serum tumor markers (STMs), alpha-fetoprotein, and human chorionic gonadotropin is an essential component of clinical evaluation as significant elevation of either STM is diagnostic for PMNSGCT. Biopsy in these cases is not only unnecessary but can be misleading due to sampling error within these typically large and heterogeneous neoplasms. We believe biopsy confirmation is only necessary in rare PMNSGCT patients presenting with normal STMs or patients with minor elevations of human chorionic gonadotropin, which can be present in pure seminomatous germ cell cancer. Histologically, these neoplasms comprise at least one nonseminomatous germ cell cancer subtype (yolk sac cancer, embryonal carcinoma, or choriocarcinoma in order of frequency), and frequently are mixed with some form of pathologic teratoma ranging from mature teratoma to teratoma with immature elements (“stromal aytpia”), and finally, to frank malignant degeneration of teratoma into the so-called “nongerm cell” cancer (sarcomas and epithelial carcinomas). Chest and abdominal CT scans are standard imaging tests for staging with other radiologic studies including positron emission tomography scan and central nervous system magnetic resonance imaging obtained on an individual basis. Gated magnetic resonance imaging or echocardiogram can be helpful to determine the presence of great vessel or cardiac involvement; however, invasion may be subtle and only apparent at the time of postchemotherapy surgical resection. We therefore have cardiopulmonary bypass capabilities available for these cases. After diagnosis and staging, surgical resection for PMNSGCT as initial therapy will rarely achieve local control and does not treat metastatic disease, present in 20 to 25% of cases. Appropriate therapy typically begins with cisplatin-based chemotherapy. Over the past 3 years we have utilized etoposide,