Clinical and radiographic characterization of primary seminomas and nonseminomatous germ cell tumors.

Background: Primary malignant mediastinal germ cell tumors (PMMGCTs) including seminomas and nonseminomatous germ cell tumors (NSGCTs) are rare, and sometimes the diagnosis is very difficult.

Purpose: The purpose of this study is to compare the clinical characteristics, biomarkers, and imaging findings of seminomas and NSGCTs and to determine whether these features could help distinguish these two types of PMMGCT.

Material and Methods: A retrospective study of 24 male patients with histopathologically proven PMMGCT was performed. We collected the information of computed tomography (CT) (the scan area ranged from the apex of lung to the costophrenic angles) and magnetic resonance imaging blood test and histology characteristics of these patients.

Results: Twelve of 24 cases were confirmed to be seminomas, whereas the other 12 cases were NSGCTs. Alfa-fetoprotein (AFP) was found to be elevated in all patients with NSGCT, whereas none of the patients with seminomas had elevated AFP level. Beta-human chorionic gonadotropin (β-HCG) level was elevated in all the patients with seminomas (seven/seven), whereas in NSGCT only two of seven patients had elevated β-HCG. Lactate dehydrogenase level was increased in five of the nine patients with seminomas, as well as in the eight patients with NSGCT. CT imaging revealed that 12 masses from the seminoma group were homogeneous, soft tissue opacity and showed minimal contrast enhancement. On the contrary, all 12 NSGCT cases showed cystic and solid masses; on contrast-enhanced CT, heterogeneous enhancement was found on the capsule of the tumor, septum, and solid masses.

Conclusion: Seminomas and NSGCT showed different profiles of tumor biomarkers and radiographic features. Evidence from serum test, histopathological analysis, and imaging should be combined to ensure the accurate diagnosis of these two types of PMMGCT.