Immunohistological description of nongestational ovarian choriocarcinoma in two female mice with conditional loss of Trp53 driven by the Tie2 promoter

Nongestational ovarian choriocarcinoma (NGCO) is a tumor of germ cell origin seldom described in nonhuman species. Few spontaneous cases are reported in macaques and mice, with the B6C3F1 strain overrepresented. This report describes 2 cases of ovarian choriocarcinoma in nulliparous female mice with conditional loss of Trp53 under the Tie2 promoter. The mouse line was maintained on a mixed genetic background including Crl: CD1(ICR) and 129X1/SvJ strains. In both cases, affected ovary was partially replaced by blood-filled lacunae lined by neoplastic trophoblast-like giant cells. Immunohistochemically, neoplastic cells expressed folate-binding protein and prolactin and were invariably negative for p53. To the authors? knowledge, this is the first report characterizing this entity in a genetically engineered mouse (GEM) line. Considering that germ cells (the cell population from which NGCO originates) constitutively express Tie2 receptor, it can be speculated that Tie2-driven deletion of Trp53 may have played a role in the development of these tumors.