[Cytogenetical study on the etiology of partial mole]

The cytogenetical etiology of partial mole (PM) was studied by means of the Q-banding technique in 49 cases during the period between Sep. 1976 and Nov. 1986. Moreover, histological examinations were performed in 39 cases concentrating on the existence of fetal components and trophoblastic hyperplasia, etc. The results were as follows. 1. Karyotype analysis showed triploidy (24 cases), normal diploidy (10 cases), trisomy (9 cases) and other anomalies (mosaic, translocation etc.) (6 cases). These results are quite different from those of many western authors, who reported that most cases of PM are triploidy. 2. The criteria of PM in Japan differ from those of WHO Scientific Group in regard to trophoblastic hyperplasia. 3. Our cases were reclassified on the basis of the definition drawn up by the WHO Scientific Group. Nevertheless, the rate of triploidy was only 54.5%, which is lower than that reported by many western authors. These results show that the development of PM cannot be explained cytogenetically at present, in contrast with complete mole.