Retroperitoneal seminoma as a first manifestation of a partially regressed (burnt-out) testicular germ cell tumor.

Regressed (burnt-out) testicular germ cell tumors (TGCT) are rare clinical situations that are clinically difficult to recognize. This 43-year-old patient was admitted because of a suspicion of prostatic carcinoma, which eventually was followed by transrectal ultrasonography and a CT scan, both of which revealed a large retroperitoneal mass. Surgery showed extensive ureteral and vas deferens infiltration. Pathology was consistent with a classical seminoma. Eventually, testes were normal on palpation but ultrasonography only revealed areas of fibrosis and microcalcifications in the left testis, which was followed by a left orchidectomy. Microscopically, there were extensive areas of fibrosis and only a 2 mm area of seminoma was demonstrated. The few areas of uninvolved testicular tissue lacked lesions of intratubular germ cell neoplasia (IGCNU). Retroperitoneal germ cell tumors are rare in the male and consequently, an origin from an occult testicular tumor should always be discarded by image analysis and eventually a biopsy. Immunologic response may be responsible for tumor involution.