Testicular Germ Cell Tumor Composed of Seminoma and Teratoma Metastasizing as Choriocarcinoma to the Lung Successfully Treated With Salvage Chemotherapy and Bone-Marrow Transplant: A Case Report.

A 25-year-old male presented to our hospital with two months of progressively worsening left arm swelling, intermittent left-sided chest pressure, and a painless right testicular mass. CT of the chest, abdomen, and pelvis revealed a large mediastinal mass, multiple lung nodules, and several large right testicular nodules. The patient underwent a CT-guided biopsy of his right lung nodule, followed by a radical right inguinal orchiectomy. The testicular biopsy revealed a mixed germ cell tumor (GCT) consisting of 97% seminoma and 3% teratoma, while the lung biopsy revealed metastatic choriocarcinoma. The patient was treated with four cycles of bleomycin, etoposide, and platinum (BEP) and showed a great clinical response, with only residual disease in his retroperitoneal lymph nodes. He was referred for retroperitoneal lymph node dissection (RPLND); however, there was a delay of several months, which led to the recurrence of his disease. He received four cycles of paclitaxel, ifosfamide, and cisplatin and showed a moderate response. He later received salvage chemotherapy with high-dose carboplatin and etoposide and underwent bone-marrow transplant, leading to complete clinical response and eradication of his disease. There are different subtypes of testicular GCTs, each with distinct pathogenesis, treatment modality, and prognosis. In this report, we discuss the case of a patient who presented with a mixed GCT consisting of seminoma and teratoma in his testicle, which had metastasized as choriocarcinoma to his lung and mediastinum. This report elucidates the potential for testicular GCTs to metastasize as a pathologically different cancer compared to the primary tumor. This phenomenon has significant clinical ramifications, as it can considerably alter a patient's treatment and prognostic outcomes.