2. Case presentation
An 18-year-old adolescent came to our medical center from a local hospital for further management of a giant anterior mediastinum mass. Four months before this admission, he made a routine health examination at local health institution and found a huge mass in the mediastinum without any clinical symptoms such as chest pain, dyspnea, or cough. For further treatment, he was referred to a comprehensive oncology hospital and malignant GCT was diagnosed by mediastinal biopsy. Therefore, combined chemotherapy with etoposide (100 mg/m2IV on days 1–5), bleomycin (30 units IV on days1, 8, and 15), and cisplatin (20 mg/m2IV on days 1–5) was subsequently initiated. However, when four cycles of chemotherapy were finished, he underwent a chest CT again which indicated that there was no obvious improvement. Hence, he received radiotherapy (specific dose was not known) at another oncology hospital and the mediastinum mass failed again to respond to radiotherapy and the tumor volume even grew since then. In our hospital, physical examination revealed a thin-built man with normal vital signs and weight loss. Superior vena cava syndrome (SVCs) such as facial edema and jugular vein distention was not observed. Respiratory, cardiac, abdominal, testicular and lymph node examination were negative.
Contrast-enhanced CT showed that a large (approximately 21.6×12.3×10.5cm3) solid mass with heterogeneous enhancement and noncalcified in the anterior mediastinum. Heart and great vessels including superior vena cava (SVC), ascending aorta, pulmonary artery and left principal bronchus were compressed and surrounded by the tumor with well-defined margin while mediastinal lymph nodes were not noted (Figure 1). Brain MRI, abdominal contrast-enhanced CT, bone scan and pulmonary function test were normal.
Laboratory investigations showed thrombocytopenia (platelets=21×109/L, normal=100~300×109/L), anemia (hemoglobin[Hb]= 92g/L, normal range=130-175g/L) and normal leukocyte count. Lactate dehydrogenase (LDH), alpha fetoprotein (AFP), β-human chorionic gonadotropin(β-HCG) and carcinoembryonic antigen (CEA) were elevated(AFP>1210ng/ml, normal<8ng/ml; β-HCG=270.48mIU/ml, normal<3.81mIU/ml; CEA=3.71ng/ml, normal<3.4ng/ml). After chemotherapy and radiotherapy, the level of AFP decreased to 69.56ng/ml and β-HCG decreased to normal (β-HCG=0.26mIU/ml). Other laboratory examinations including renal, hepatic, coagulation function were within acceptable limits. Therefore, the patient underwent surgical resection of the tumor after informed consent was obtained from the patient.
A giant solid mass with intact capsule was observed macroscopically. In the mass, most of the components were solid with local necrosis and multiple cysts. Two mediastinal lymph nodes were observed with a diameter of about 0.8~0.9cm. At the same time, a piece of pericardium attached to the tumor with a size of about 3.6cm×2.2cm was also observed. Microscopically, the tumor was consisted of epithelial tissue, cartilage tissue, skeletal muscle tissue and other mesenchymal tissue, part of which were presented as immature or malignant morphology (Figure 2). Immunohistochemical staining demonstrated that cytokeratin (CK), epithelial membrane antigen (EMA), smooth muscle actin (SMA), desmin (Des), MyoD 1 and Myogenin were positive while AFP and HCG were negative indicating that the large mass was an immature teratoma with poorly differentiated squamous cell carcinoma and sarcoma malignant transformation.