OBJECTIVE: Mediastinal germ cell tumors are rare and few large-scale studies on mediastinal germ cell tumors are reported. We aimed to investigate the clinical characteristics and survival outcomes of patients with mediastinum germ cell tumors in Japan.
METHODS: A hospital-based cancer registry data in Japan was used to identify and enroll patients diagnosed with mediastinal germ cell tumors in 2012-2013. The datasets were registered from 80 institutions.
RESULTS: The selection criteria were met by 123 patients, the majority of whom were male. The median age at diagnosis was 39 years (range 25-89 years) and the most common age groups at diagnosis was 30-39 years, followed by 40-49 years and ≥ 50 years. The histology of non-seminoma (55.3%) was slightly more frequent than that of seminoma (44.7%). The most common histological subtype in non-seminoma was yolk sac tumor, followed by mixed germ cell tumor. The 5-year survival of seminoma and non-seminoma were 96.4% and 57.3%, respectively (p < 0.001). Non-seminomatous mediastinal germ cell tumors, malignant teratomas, mixed germ cell tumors, and yolk sac tumors had comparable survival rates, while those with choriocarcinoma showed the worst prognosis.
CONCLUSIONS: This is the first report showing the clinical characteristics and survival outcomes of mediastinal germ cell tumors in Japan using a real-world large cohort database.

Vasculogenic mesenchymal lesions (VMLs) of germ cell tumor origin are thought to originate in postpubertal-type yolk sac tumor components and include a spectrum of lesions from teratoma with vasculogenic stroma (TVS), to low and high-grade vasculogenic mesenchymal tumors (VMTs). VMLs exhibit rudimentary to well-developed neoplastic vessels within primitive mesenchyme, being considered a neoplastic reiteration of embryonic vasculogenesis in the splanchnic mesoderm of the yolk sac. They occur in patients with primary mediastinal germ cell tumors after chemotherapy, and a subset progresses to \"somatic-type\" sarcomas [including angiosarcoma (AS)], with high-grade VMTs likely portending a higher risk. Recently, we encountered a low-grade VMT that progressed to metastatic AS during follow-up. In this case, both the low-grade VMT and the subsequent AS demonstrated p53 overexpression, suggesting that p53 alterations may precede histopathologic transformation. To test this hypothesis, we evaluated neoplasms representing the entire spectrum of VMLs using p53 immunohistochemistry (IHC; clone DO-7, Dako). Overexpression was defined as nuclear positivity in > 80% of neoplastic cells. Because the distinction between high-grade VMT and AS can be subjective in some cases, they were grouped together in a single category. Thirty-nine VMLs were assessed: 16 high-grade VMT/AS, 19 low-grade VMT, and 4 TVS. Patient age ranged from 19 to 46 years (mean, 30 years; male = 97%). Four high-grade VMT/AS and one low-grade VMT showed p53 overexpression (5/39 VMLs, 13%; 4/16 high-grade VMT/AS, 25%). These tumors included 1 unequivocal AS and 1 high-grade VMT/AS with progression to rhabdomyosarcoma. The only low-grade VMT with p53 overexpression demonstrated progression to AS. Another high-grade VMT that progressed to sarcoma demonstrated p53 overexpression in the sarcoma component, but it was excluded because the VMT was not represented in the material available at the time of the study. Lesions with intratumoral grade heterogeneity (classified based the highest grade), demonstrated more pronounced p53 overexpression in the high-grade components. P53 overexpression is associated with disease progression in a subset of VMTs and may precede morphologic transformation to sarcoma. Routine evaluation of VMTs with p53 IHC seems justified, with overexpressors likely requiring an close clinical surveillance.

BACKGROUND: Mediastinal teratoma is an uncommon disease, nevertheless they represent the most common mediastinal germ cell tumors. It may grow silently for several years and remain undiagnosed until the occurrence of a complication.
OBJECTIVE: The main aim of this article is to illustrate the silent evolution of an anterior mediastinal teratoma for over 70 years without presenting any notable complications.
METHODS: We present the case of a 70-year-old female, treated for hypertension referred to our department for managing a voluminous mediastinal mass, discovered fortuitously by a general practitioner in a chest X-ray. The anamnesis didn\'t relate any chest pain, cough, dyspnea nor hemoptysis. The clinical examination, in particular pleuropulmonary, was unremarkable. The workup (Chest X-Ray and CT scan) demonstrated a voluminous pleural mass at the expense of the right mediastinal pleura, rounded in shape, with calcified wall and fluid content. Blood tests did not demonstrate eosinophilia, and hydatid IgG serology was negative. serum human chorionic gonadotropin (hCG) and alpha fetoprotein (AFP) levels were found to be normal. The patient subsequently underwent a right posterolateral thoracotomy with resection of the lesion. The mass was dissected very carefully and then resected in toto. The macroscopic and microscopic histological examination demonstrated a mature cystic teratoma. Surgical resection was an adequate treatment and the prognosis was excellent for the patient.
CONCLUSIONS: Cystic mature teratomas are rare thoracic tumors, often recognized by radiological examination. This article relates the silent evolution that a teratoma could have, and the late appearance of symptoms that it could have.

Germ cell tumors (GCTs) are the most common malignancies in men aged 15-35 years. Five percent of malignant GCTs are of extragonadal origin, and the most common extragonadal location for GCTs in adults is the mediastinum. Like other mediastinal tumors, mediastinal GCTs may cause compression or invasion of vital mediastinal structures, resulting in respiratory or hemodynamic compromise. Right ventricular failure following positive pressure ventilation of such patients is called mediastinal mass syndrome (MMS). This report presents a case of a GCT complicated by cardiac arrest shortly after starting positive pressure ventilation, which was successfully resuscitated. Few previous reports demonstrated a successful outcome of MMS. This report highlights the importance of a multidisciplinary approach for such scenarios in light of the scanty literature and lack of clear guidance and the significance of starting chemotherapy in a timely manner.

Teratomas are a type of germ cell tumor that may contain several different types of tissue. Neurofibroma is a benign peripheral nerve sheath tumor with the plexiform type being pathognomonic for neurofibromatosis type 1. We report a case of a 33-year-old woman with a background of Neurofibromatosis type 1 who presented with left-sided chest pain and shortness of breath. She was diagnosed with a large mediastinal mass which was confirmed from a CT-guided biopsy as neurofibroma. Following a multidisciplinary team discussion, she underwent mediastinal mass resection and the final histopathology report revealed mediastinal mature teratoma.

Mediastinal masses can present as a medical emergency when there is central airway obstruction, superior vena cava (SVC) syndrome, direct mediastinal extension of tumor, or obstruction of the central pulmonary vasculature. Diagnostic evaluation may include the need for invasive tissue biopsy under anesthesia, which can pose several distinct risks for patients. Among the many etiologies of mediastinal tumors, primary mediastinal germ cell tumors are a rare form with a favorable prognosis.

Primary mediastinal mixed germ cell tumors (PMMGCTs) are rare, aggressive tumors that, at diagnosis, are typically metastatic. A 22-year-old male with a three-month history of cough, chest pain, and fever presented to our outpatient department. Clinical examination showed reduced left-sided air entry in the left hemithorax, with a non-palpable left testis. Imaging suggested a large anterior mediastinal mass and an absent left testis. Multiple biopsies revealed only necrotic tissue, and laboratory investigations showed elevated alpha-fetoprotein levels. A provisional diagnosis of mediastinal germ tumor was made, and surgical excision was planned given absent nodal or distant metastasis. Intraoperatively, a densely adherent bosselated mass was found. A biopsy revealed a mixed germ cell tumor with a predominant seminoma component and chemotherapy with cisplatin and ifosfamide was advised. However, the patient was lost to follow-up after one cycle. PMMGCTs possibly occur due to reverse migration. These tumors warrant an early diagnosis due to their highly aggressive nature. A multimodal approach with chemotherapy with surgical resection is recommended. Our case sheds light on the possible mechanism and emphasizes the impact of early diagnosis.

OBJECTIVE: Primary mediastinal non-seminomatous germ cell tumors (PMNSGCTs) are occasionally complicated by a hematologic malignancy, as with somatic-type malignant tumors called germ cell tumors with somatic-type malignancy (GCTSTM) and are known to have a poor prognosis.
METHODS: Data obtained between September 1997 and February 2020 for patients with mediastinal germ cell tumor at our institution were retrospectively analyzed. Key outcome measures included survival rates and the clinical features of non-seminoma cases.
RESULTS: Of 16 patients, 9 had pure seminoma, and 7 had non-seminoma. At the median follow-up of 56.2 months, the 5-year survival rate was significantly higher in patients with seminoma (100%) than in those with non-seminoma (37%) (log-rank test, p=0.0153). Regarding PMNSGCT, two patients evolved into GCTSTM and three had concomitant hematological malignancies.
CONCLUSIONS: Patients with PMNSGCTs, GCTSTM complications, and hematologic malignancies showed poor survival, suggesting the need for the development of treatment strategies.

Mediastinal germ cell tumor (MGCT) is a relatively rare tumor. Complete resection after chemotherapy is a standard treatment against this disease. However, the risk factors of incomplete resection are unclear. Therefore, we analyzed survival rates and risk factors for incomplete resection based on preoperative imaging.
We retrospectively reviewed the medical records of patients (n = 56) with MGCT operated at National Cancer Center Hospital, and analyzed preoperative computed tomography (CT) data in terms of relationship of the tumor and vessels, and investigated survival rate and risk factors for incomplete resection.
A total of 56 patients underwent resection of MGCT. The 5-y progression-free survival (PFS) and overall survival (OS) were 79% and 83%. In multivariate analysis, complete resection was the only significant prognostic factor for better PFS (hazard ratio (HR) = 9.083, P= 0.00021) and OS (HR = 5.519, P= 0.0445). The preoperative CT finding of arteries (including the aorta, right brachiocephalic artery, left common carotid artery, and left subclavian artery) surrounded by the tumor was a predictor of incomplete resection (odds ratio = 10.089, P= 0.049).
Complete resection is essential for improving the survival of MGCT, and the risk stratification using preoperative CT imaging brings important information to achieve the complete resection.

A 29-year-old male developed acute onset severe shortness of breath and fevers and was found to have a 17 cm anterior mediastinal mass with immature teratoma and possible mixed germ cell tumor on biopsy. He remained hospitalized during neoadjuvant cisplatin-based chemotherapy due to compressive symptoms from his mass and neutropenic fevers. Despite 3 cycles of therapy, his tumor mildly increased in size. After multidisciplinary discussion, he underwent urgent en bloc resection with a right hemi-clamshell incision. His postoperative course was uncomplicated and he was discharged to home within a week. His final pathology demonstrated mixed germ cell tumor.