MALIGNANT TROPHOBLASTIC NEOPLASMS WITH DIFFERENT MODES OF ORIGIN

The genetic origin of 24 trophoblastic neoplasms was determined using PCR polymorphisms. Based on pregnancy history, these tumors included n ine postmolar trophoblastic tumors, 12 tumors preceded by live birth o r abortion, and three nongestational tumors. Androgenetic origin was d efined in eight postmolar trophoblastic tumors, and the remaining one might have arisen from a normal fertilization. Six tumors retained gen etic features carried by the homozygous complete mole. Two tumors show ed PCR polymorphism compatible with that of the heterozygous complete mole. All 12 tumors in the second class had alleles of both paternal a nd maternal contribution. However, discordance of sex between the ante cedent pregnancy product and the tumor was recognized in three chorioc arcinomas. The absence of paternal contribution suggested a parthenoge netic origin of three nongestational choriocarcinomas. The findings th at PCR polymorphisms were either homozygous in certain loci or heteroz ygous in others may mean that the tumor was derived from a germ cell a fter meiosis I. As a result, at least three subtypes with different mo des of origin were demonstrated in the 24 trophoblastic tumors. These findings underscore the importance of precise genetic marker analyses in a large series to clearly identify clinical and biologic characteri stics of each subset of tumors.