Seminoma occasionally contains foci of trophocarcinoma (embryonal carcinoma), or else has histologic features of aggressive growth. The resultant variants are classified into: anaplastic seminoma, borderline seminoma, and seminoma with trophocarcinoma. The latter variant is characterized by specific histologic features and, compared with pure seminoma, by more aggressive clinical behavior, larger required tumor lethal radiation dose, and lower survival rate. The intimate association of primordial trophoblastic structures with seminoma is of histogenetic interest.