Transformation of a Testicular Teratoma to an Aggressive Primitive Neuroectodermal Tumor

We present a case of a 36-year-old male found to have a nonseminomatous germ cell tumor (NSGCT) with alpha-fetoprotein levels (AFP) of 737.9 ng/mL and beta-human chorionic gonadotropin (β-HCG) of 692 IU/mL. Pathology analysis after left orchiectomy showed a mixed germ cell tumor with 20% embryonal carcinoma, 20% yolk sac tumor, and 60% teratoma. The patient's AFP levels normalized three months after surgery. Chemotherapy was proposed, but the patient declined. Two years post orchiectomy, lytic bone lesions were discovered on a surveillance CT. A bone marrow biopsy (BMB) showed neural differentiation consistent with metastatic primitive neuroectodermal tumor (PNET) arising from the previous testicular germ cell tumor. Treatment for the PNET included vincristine, doxorubicin, cyclophosphamide, and ifosfamide/etoposide mesna. Two months later, a repeat BMB showed minimal tumor cells. The patient also underwent a tandem autologous stem cell transplant with carboplatin/etoposide conditioning and adjuvant etoposide and the subsequent PET/CT scan showed a response to the above treatment. Clinical stage I of NSGTs can often be cured with orchiectomy; the challenge is identifying high recurrence risks. This is a unique case of NSGCT transforming to PNET, an aggressive tumor with a poor prognosis given the limited response to standard chemotherapy of platinum-based drugs. Our patient underwent chemotherapy and an autologous stem cell transplant, which proved to be effective in high-risk diseases. There are no established guidelines for the treatment for malignant transformation of testicular teratoma into PNET. The regimen for our patient yielded promising results. Our aim is to highlight a regimen that can be utilized for this rare aggressive neoplasm.