Primary extragonadal germ cell tumours: Real-world data from a high-volume centre

To provide improved evidence for treatment recommendations, this study analysed real-world data on the characteristics, treatment and prognosis of primary extragonadal germ cell tumours (EGCTs), a very rare cancer entity that shares histological features with testicular GCTs (TGCT).

This retrospective study analysed data from 34 patients with mediastinal or retroperitoneal EGCTs treated at a high-volume centre between 2015 and 2025. Probability of overall survival (OS) and relapse-free survival (RFS) was assessed using Kaplan-Meier curves.

A primary retroperitoneal and primary mediastinal GCT was diagnosed in 23 (68%) and 11 (32%) patients, respectively. Median patient age was 41.1 years, and 62% were non-seminomatous in origin. Thirty-three (97%) patients received chemotherapy according to the IGCCCG prognostic group, and 15 (44%) underwent surgical intervention (4 primary RPLND, 8 post-chemotherapy RPLND, 3 secondary orchiectomy). Thirteen patients (44.9%) who completed chemotherapy experienced a relapse after a median of 0.79 years, and six of them died. In patients with primary mediastinal seminoma, 3-year RFS and OS were 100% as compared to 71% 3-year OS in patients with primary retroperitoneal non-seminoma and 46% 3-year RFS in patients with primary mediastinal non-seminoma.

The prognosis for primary mediastinal seminoma appears favourable, while non-seminomatous EGCT shows poorer outcomes. Additionally, primary retroperitoneal seminomas demonstrate promising survival rates, whereas primary retroperitoneal non-seminomas demonstrate the lowest OS rates.