Under-registration of gestational trophoblastic disease in the Swedish Cancer Registry.

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.