Conclusion
Primary yolk sac tumors are rare in the adult population. We described a case of a 40-year-old male here who presented with left testicular swelling and was found to have a primary yolk sac tumor with extension into the left retroperitoneal space as well as bilateral pulmonary metastasis. He was treated with BEP chemotherapy with good response and has gotten orchiectomy post treatment for residual disease. This report highlights the necessity of accelerated work up required for adult post pubertal patients presenting with possible testicular tumors given the possible aggressive nature of the underlying disease.