Differentiation of human testicular embryonal carcinoma and teratocarcinoma grown in nude mice and soft-agar cultures.

The differentiation pattern of two human germ cell tumors, grown in nude mice and in vitro is described. Tumor A was an embryonal carcinoma (EC) of borderline histology with characteristics of yolk sac tumor and of seminoma; tumor B was a teratocarcinoma with yolk sac elements and syncytiotrophoblastic giant cells. The morphology of an EC as well as cytogenetic characteristics were maintained during 20 passages in nude mice from tumor A and over 11 passages from tumor B. Tumor A did not grow in vitro. Cell suspensions prepared from xenografted tumor B grew into cystic embryoid bodies in semi-solid tissue culture medium. These embryoid bodies showed cuboidal and flattened cells with microvilli, junctional complexes, peripheral microfilaments, and annulated lamellae, reminiscent of the 'inner cell mass' of a blastula and of endoderm, respectively. When such colonies were transplanted into nude mice, however, only tumors with the morphology found in the transplants appeared.