These rare tumors, although formerly fairly common in South East Asia, now appear to be declining in incidence.
Histology, classification and diagnosis
Choriocarcinoma arises from the trophoblastic epithelium of the placenta. It frequently, but not invariably, follows a hydatidiform mole, and invades maternal tissues. Very rarely, these cancers may arise in the mediastinum, the ovary, and the testis.
The International Classification of Diseases (ICD) regards only tumors denoted as choriocarcinomas as being classifiable to this rubric. The invasive or so-called malignant hydatidiform mole (chorioadenoma destruens) is assigned to tumors of uncertain behavior. The diagnostic criterion which distinguishes these two entities is the presence of chorionic villi in the latter. Diagnosis is made either through examination of endometrial scrapings or metastatic deposits, or through demonstration of increased chorionic gonadotrophin in urine.
Incidence and time trends
The incidence rates for this tumor are usually very low, around 0.1 or less. They tend to be somewhat higher in South East Asia, for example, in Rizal province, of the Philippines (0.7) and in Chinese in Singapore and Shanghai (0.5).
Some registries, however, include malignant mole with choriocarcinoma. Shanmugaratnam et al. (1971) calculated age-standardized rates for histologically diagnosed choriocarcinoma for Chinese and Malays in Singapore as 1.0 and 1.2 respectively. The rates for histologically diagnosed malignant trophoblastic disease (both choriocarcinoma and invasive mole) were 18 per 100,000 live births and still-births. Comparable figures for Connecticut, Norway and Sweden were 2, 6 and 4.