The patient in our case presented with a seminoma described histologically with an additional separate nodule which may have represented a burnt-out yolk sac tumor; however, both preoperatively and postoperatively, their serum AFP levels were elevated. Despite receiving bleomycin, etoposide, and cisplatin chemotherapy and showing no evidence of disease recurrence, this patient's serum AFP remained elevated. This evidence concerns the gene AFP and yolk sac tumor.