[Metachronous testicular tumor of an extragonadal germ cell tumor].

Introduction: Approximately 5 - 7 % of germ cell tumors are of extragonadal origin. Biology and genetics are unclear, especially when the primary location is in the retroperitoneum. Chemotherapy is the initial treatment of choice for extragonadal germ cell tumors (EGGCTs), followed by surgical resection of the residual tumor mass. A primary testicular tumor must be ruled out by sonographic investigation and biopsy. The rate of metachronous testicular cancer in men with primary EGGCT is largely unknown.

Case Report: We present the first patient in the literature who developed a metachronous testicular cancer 10 months after primary occurrence of EGGCT in the retroperitoneum.

Conclusions: This case report emphasizes the importance of follow-up examinations of patients with primary EGGCTs. They should include careful sonographic investigation of the testis in order to detect metachronous testicular cancer early. Suspicious findings require open surgery biopsy. Intraoperative histopathology can be false-negative for cancer detection, as an immunohistochemical examination is not available.