Maediastinal germ cell tumors: analysis using hospital-based cancer registry data in Japan.

Objectives: 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.