DIPLOID HYDATIDIFORM MOLES WITH FETAL RED-BLOOD-CELLS IN MOLAR VILLI .1. PATHOLOGY, INCIDENCE, AND PROGNOSIS

It is believed that fetal development does not occur in complete mole (CM); when present, it is usually interpreted as proof of partial mole (PM), in most cases a triploid conception with a low incidence of per sistent trophoblastic disease (PTD). However, histological examination of 3180 moles in 8 years showed 60 moles (1.8 per cent) with features of CM and either embryonic tissues or amnion in the sample. Plow cyto metry (FC) in 40 showed diploid complement in all. In ten of the 40, t here was evidence of a twin; in 17, there was only amnion,,which could belong to a twin; in the remaining 13, there was no evidence of a twi n and nucleated fetal red blood cells (FRCs) were seen within molar ve ssels in ten (0.3 per cent). Seven of the 40 patients (17.5 per cent) and one of the ten with FRCs in villi (10 per cent) developed PTD, an incidence comparable to that of CM. Genetic studies in seven of these ten are reported separately. Finding fetal tissues with a mole or FRCs in molar vessels is not enough to classify it as PM, since it can be a CM with a twin, fetal development in CM, or possibly a third type of mole. These rare diploid moles with fetal tissues have histological a ppearances and prognosis similar to those of CM.