Genetics and biology of human ovarian teratomas. III. Cytogenetics and origins of malignant ovarian germ cell tumors.

This report presents cytogenetic data on three cases of malignant ovarian germ cell tumors. All were diagnosed as malignant teratoma; case 1 with yolk sac elements; case 2 with elements of endodermal sinus tumor, embryonal carcinoma, and choriocarcinoma; and case 3 with yolk sac elements and embryonal carcinoma. Metaphase cells from each tumor, and normal tissue from the host, were karyotyped and scored for centromeric heteromorphisms in an attempt to determine the mechanism of origin. The karyotypes were 79,XXX,+1,+3,-6,+8,+12,+14,-15,+17, +20,+21,+22;49,XX,+8,+12,+22; and 48,XX,+3,+14, respectively. The analysis of centromeric heteromorphisms and DNA fingerprints of host and teratoma using the M13 probe revealed that one case originated from a germ cell before the first meiotic division. Normal host tissue was not available in case 2, but several centromeric markers were heterozygous in the tumor, indicating either meiosis I error or complete failure of germ cell meiosis. In the third case the centromeric heteromorphisms that were heterozygous in the host appeared to be homozygous for certain chromosomes and heterozygous for others in the tumor. These results suggest that germ cell teratomas could arise by the fusion of two ova.