[Retroperitoneal germ cell tumor with testicular calcification indicating tiny testicular origin: consideration of the origin of retroperitoneal germ cell tumors: report of two cases].

: Two cases of germ cell neoplasm retrospectively considered to have been of testicular origin are reported. Case 1. A 19-year-old male with brain, liver and retroperitoneal tumors was diagnosed with yolk sac tumor by retroperitoneal tumor biopsy. After multidisciplinary treatment, a region of calcification was detected in the left testis on scrotal sonography and left high inguinal orchiectomy was performed. Case 2. A 57-year-old male with neck, lung and retroperitoneal tumors was diagnosed with yolk sac tumor by supraclavicular biopsy. From initial examination, scrotal sonography revealed a small calcified lesion in the right testis. After chemotherapy, high inguinal orchiectomy and retroperitoneal lymphadenectomy were simultaneously performed. Pathologic evaluation of these testicular specimens revealed calcification and a fibrous scar in correspondence with the clinical diagnosis. These changes were considered as scars of the primary testicular tumor due to burned-out tumor or the result of reaction to chemotherapy. Since a primary tumor of testicular origin may exist in the extragonadal germ cell tumor, it is important to examine the intrascrotal contents in detail in the case of so-called extragonadal germ cell tumors with palpably normal testes. In such cases, there are two possible conditions, an occult testicular tumor and a burned-out testicular tumor. We briefly reviewed 42 such cases in the Japanese literature. It appears that there are very few true extragonadal germ cell tumors, and that the possibility of primary testicular origin metastasizing from viable occult testicular tumor or burned-out testicular tumor with spontaneous regression is high in retroperitoneal germ cell tumors.