Ovarian Teratomas in Mice Lacking the Protooncogene c‐mos

Parthenogenesis has been suggested to be tightly coupled with development of ovarian teratomas. Indeed, ovarian tumors developed in c‐mos‐delieicnt female mice, which are characterized by the parthenogenetic activation of oocytes. The tumors appeared at a frequency of 30% between 4 and 8 months of age, and did not develop in younger or older mice. Most of the tumors were benign and consisted of multi‐focal cysts most notably with mature ectodermal components, but also with mesodermal and endodermal components. One among 17 tumors observed consisted of extraembryonic tissues alone, and two bore malignant components with metastasis to peritoneal organs. The results strongly suggest the involvement of c‐mos mutations in human germ cell tumors.