An epidemiological study with the aim of establishing the incidence of hydatidiform mole, persistent trophoblastic disease and choriocarcinoma in Stockholm County was performed. Based on the regional cancer registry and hospital registers, the incidence for 1975-1988 was calculated for the number of deliveries as well as the total number of pregnancies. Of the molar pregnancies, 6% were treated with chemotherapy because of invasive mole or choriocarcinoma. Non-molar choriocarcinoma occurred in 1/33,717 deliveries. Difficulties in assessing the incidence of gestational trophoblastic disease are discussed.
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 incidence 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 Greeland. 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 predisposition.
The paper presents a study of completeness of registration of hydatidiform mole and gestational trophoblastic neoplasia in the Swedish Cancer Registry. The study is based on patients treated in Stockholm County, Sweden from 1971 through 1986. Non-notified cases were identified through a computerized register covering nearly all hospital admissions in the region and local hospital patient register. The results show that 25% of the cases with a diagnosis of hydatidiform mole were not included in the cancer register. Of all patients treated for trophoblastic malignancy, 66% were not recorded in the Cancer Registry. The frequent absence of histopathological confirmation in cases with malignant trophoblastic disease was probably the main factor contributing to the observed under-registration. The study indicates that the Swedish Cancer Registry alone does not provide sufficient data for studies on the incidence of gestational trophoblastic disease.
