[Pathology of the placenta. XII. Tumors of the umbilical cord and placenta].

Benign and malignant tumours of the umbilical cord and placenta are the topics covered in Part XII of this general account under the above heading. Angiomas, angiofibromas and teratomas, all of them of rare occurrence, are the benign tumours, with the chorioangioma being the best known of them. The trophoblast tumours proper include chorionic epitheliomas and choriocarcinomas. While histological differentiation is not possible between these two, they still are biologically benign or malignant. They may develop in the wake of normal pregnancy or abortion or hydatidiform mole. Southeast Asia is a geographically preferred region for hydatidiform mole and chorionic epithelioma. Differentiated growth behaviours of trophoblast tumours are attributable to immunological aspects. It is certainly a rare event to have a high degree of tissue compatibility (HLA antigens) between tumour and maternal organism. This may at least offer an explanation for the low incidence of choriocarcinomas in the northern hemisphere. In Southeast Asia, efforts should be made to clear up the causative background of high incidence of hydatidiform mole, since the latter most probably is the basis for development of choriocarcinoma.