Morphological and immunological characteristics of a rat choriocarcinoma

A post-gestational rat choriocarcinoma has been studied for its immunological and morphological characteristics. The tumor can be transplanted in syngeneic (WKA/H rats) as well as in allogeneic rats (BN, R/A). Even after immunization of the allogeneic hosts with tissues of the WKA/H rats, the development of the tumor was not inhibited. This neoplasm is composed of giant cells, surrounding spaces filled with blood, and of proliferating cytotrophoblasts. Ultrastructurally, these cells are very similar to those found in normal rat placenta. In some rats lung metastases were also observed. The tumor is hormonally active as demonstrated by proliferation of and secretions from the mammary glands in tumor-bearing animals and by the presence of delta 5-3 beta-hydroxysteroid dehydrogenase in the giant cells of the neoplasms. These 2 findings indicate that the rat choriocarcinoma cells secrete lactogen and might produce progesterone, like cells of rat placenta. All the described features of this tumor point to its similarity to human choriocarcinoma.