Elevated serum alphafetoprotein and seminoma clinical evidence for a histologic continuum?

We report the clinical courses of patients with histologically “pure” seminomas, but with elevated circulating levels of alpha-fetoprotein (AFP). Histologic review of these cases supports the concept of a continuum of cellular differentiation between classical seminoma and yolk sac carcinoma, as has recently been described in xenografted human germ cell tumors. This may explain the occurrence of nonseminomatous metastases in patients with “pure” seminomas and the occasional failure of surgery and conventional irradiation to achieve cure in patients with seminomas apparently localised to the testis.