From 1950 through 1974, 37 cases of hydatidiform mole not followed by malignancy and 11 cases of invasively growing trophoblastic tumors (IGTT) occurred among indigenous Greenlandic women. The overall incidence of benign mole was 1:850 births, only slightly higher than most incidences in low-risk areas like Western Europe, North America, Australia, and Israel. In contrast, the overall incidence of IGTT, 1:2861 births, and the minimum incidence of histologically confirmed choriocarcinoma, 1:5245 births, are among the highest population-based incidences on record. A marked increase in incidence of both hydatidiform mole and IGTT was found late in reproductive life. A recent high incidence of mole among teenagers increased the incidence with statistical significance during the latest 10 years, whereas maximum incidence of IGTT was found in 1960-64. A strong association existed between hydatidiform mole and IGTT. During the study period Greenlandic women with mole had a 20% risk of developing IGTT and 64% of IGTT cases were preceded by molar pregnancy. Four cases of benign mole, but no case of IGTT, occurred among the small group of Danish women living in Greenland. The incidence, 1 mole:685 births, was higher than among the indigenous population, although the latter had a lower socio-economic status. The reason for the high occurrence of IGTT among indigenous Greenlanders remains unknown. The predominating HL-A 9 antigen could conceivably reflect a genetic predispositon. © 1979 Springer-Verlag.
