SPONTANEOUS OVARIAN CHORIOCARCINOMA IN TWO B6C3F₁ MICE

Abstract

This paper describes spontaneous ovarian choriocarcinoma in two B6C3F₁ mice used in toxicity studies. One animal (case 1) was sacrificed at eight weeks of age, and the other one (case 2) was found dead at sixty-seven weeks of age. Macroscopically, a dark red dot measuring approximately I mm in diameter (case 1) and hematoma-like enlargement (case 2) were observed in the ovary. Microscopically, in case I, the neoplasm was fully packed with tumor cells and erythrocytes. The tumor cells were round to oval giant cells with abundant, faintly basophilic cytoplasm containing PAS positive granules. In case 2, some small and two large hematocysts were present. The hematocysts contained a large number of erythrocytes and a small number of tumor cells. The tumor cells were oval to elongated giant cells with abundant, basophilic cytoplasm. Immunohistochemically, tumor cells in both cases were positive or weakly positive for human placental lactogen (HPL), human chorionic gonadotrophin (HCG), and human specific beta-1 glycoprotein (SP-1). Both cases were considered to be originated from germ cells since those female animals were virgin.