Differentiating a primary retroperitoneal seminoma from a metastatic testicular tumor with an occult testicular primary or a burned out testicular cancer remains difficult. We present a case of a burned out tumor. The patient had a retroperitoneal seminoma with ultrasonically and pathologically demonstrated abnormalities in both testes, but without evidence of tumor. The patient received chemotherapy and underwent surgery of the residual retroperitoneal mass and bilateral orchiectomy. All surgical specimens were negative for testis cancer.
Conclusion: Primary extragonadal germ cell tumors in the retroperitoneum are a rare entity. The presence of a retroperitoneal tumor with ultrasonographical abnormalities in testicular evaluation should be considered as a metastases of a burned out testicular cancer, and biopsy is mandatory. Surgical evaluation and orchiectomy should be evaluated in a individual setting.