Object: Intracranial germ cell tumors (GCTs) frequently present with bifocal lesions in both the suprasellar and pineal areas. The pathogenesis of these bifocal GCTs has been the subject of controversy. Bifocal GCTs may be caused by synchronous tumors or by metastatic spread of tumor cells from one site to the other. The prognosis associated with bifocal GCTs has also been a cause of concern.
Methods: The authors constructed a single-institution patient cohort comprising 181 patients with intracranial GCTs. The clinical characteristics of bifocal GCTs were compared with those of suprasellar and pineal GCTs.
Results: Bifocal GCTs were observed in 23 patients (12.8%). Eighteen patients presented with bifocal GCTs that were diagnosed as germinomas, but 5 patients exhibited mixed GCTs. Analyses of age distributions and comparisons of tumor sizes were compatible with a model of a metastatic origin of bifocal GCTs. Eleven patients (47.8%) presenting with bifocal GCTs exhibited tumor seeding at presentation. Tumor seeding was significantly associated with bifocal lesions (p < 0.001). Patients with bifocal germinomas showed significantly shorter event-free survival and overall survival than did those presenting with germinomas from a single site of origin.
Conclusions: Bifocal GCTs are not restricted to germinomas, as had been previously reported, but do include mixed GCTs. The authors hypothesize that bifocal GCTs may result from the metastatic spread of suprasellar or pineal GCTs. The bifocal presentation of germinomas may be a poor prognostic sign and should alert clinicians to the possibility of a disseminated disease.