We analyzed 3 cases of malignant ovarian germ cell tumors (MOGCTs), comprising 1 dysgerminoma and 2 immature teratomas, by banded chromosome analysis and by in situ hybridization (ISH) using a chromosome 12p painting probe. We found evidence of 12p abnormalities in two of them. A possible common genetic pathway of origin of a subset of MOGCTs with testicular germ cell tumors (TGCTs) is discussed.