This is a mixed testicular tumor. Mixed patterns occur in 60% of testicular tumors, with the most common pattern being teratoma (not present in this patient), embryonal carcinoma, yolk sack tumor, and hCG-containing syncytiotrophoblast. This patient's tumor also contains elements of seminoma. The prognosis of these tumors is determined by the presence or absence of more aggressive elements, notably choriocarcinoma. Choriocarcinoma contains both syncytiotrophoblast and cytotrophoblast. Embryonal carcinoma is characterized by sheets of undifferentiated cells with focal glandular differentiation. Seminoma shows lobules containing large cells with watery cytoplasm. Ref: Wyatt C., Butterwoh IV J.F., Moos P.J., Mackey D.C., Brown T.G. (2008). Chapter 17. Pathology of the Male and Female Reproductive Tract and Breast. In C. Wyatt, J.F. Butterwoh IV, P.J. Moos, D.C. Mackey, T.G. Brown (Eds),Pathology: The Big Picture.