[Vitelline components in teratomas and serum alpha-1 fetoprotein]

Serum alpha1-fetoprotein (AFP) had been determined in 31 patient with (mostly malignant) teratomas before or immediately after operation, and later in the evolution of 3 other cases with clinical evidence of recurrence or metastases. Without knowledge of these serum AFP levels, histological slides of the same 34 teratomas were reexamined, especially for the presence of yolk sac components. Two pure yolk sac tumors and 6 teratomas containing yolk sac structures were associated with serum AFP levels above 500 ng/ml. Teratomas without yolk sac structures were associated with normal serum AFP levels (i.e. 10-500 ng/ml) in 14 cases, and high serum levels (i.e. above 500 ng/ml) in one case. Histologic analysis of the 14 cases with slightly elevated AFP levels did not reveal tissue possibly responsible for the low but nevertheless abnormal AFP synthesis. High AFP levels, which are easily detectable by counter-current immunoelectrophoresis, are, however, highly specific for the yolk sac tumor or the yolk sac component of teratomas, and hence suggest that this extra-embryonic structure should be distinguished from other teratoma components.