PREVIOUS HYDATIDIFORM MOLE IDENTIFIED AS THE CAUSATIVE PREGNANCY OF CHORIOCARCINOMA FOLLOWING BIRTH OF NORMAL TWINS

For appropriate clinical management of patients with gestational troph oblastic tumors it is important to ascertain both the nature of the ca usative pregnancy and the time interval between that pregnancy and the diagnosis of the tumor. It has been shown that the immediately antece dent pregnancy may not be the causative pregnancy in some cases of cho riocarcinoma, particularly where there is a history of molar pregnancy . We report further studies of a case where the causative pregnancy wa s shown to be a hydatidiform mole, not the immediately antecedent norm al term pregnancy. We describe the use of the polymerase chain reactio n (PCR) to amplify short tandem repeat polymorphisms in DNA prepared f rom pathologic blocks of the patient's previously recognised molar pre gnancy. A comparison of these polymorphisms with those in the parental and tumor DNA has enabled us to confirm that this hydatidiform mole w as indeed the causative pregnancy. Molecular genetic techniques provid e a rapid method of determining whether a choriocarcinoma is gestation al and, if so, identifying the causative pregnancy.