Retroperitoneal germ cell tumor diagnosed by endoscopic ultrasound-guided fine needle aspiration.

Isolated extragonadal germ cell tumors can be primary in nature or metastatic from a burned out testicular cancer. Accurate diagnosis is critical as appropriate therapy can be highly curative. We present the case of an isolated extragonadal germ cell tumor in the retroperitoneum diagnosed by endoscopic ultrasound-guided fine needle aspiration. This case underscores the importance of considering germ cell tumors in the differential diagnosis of an unexplained retroperitoneal mass, particularly since immunophenotypic staining may be necessary to establish the diagnosis.