Possible liver cell differentiation in testicular germ cell tumours.

Germ cell tumours may imitate various structures of the developing embryo and foetus. Certain structures have, however, very rarely or never been observed in these tumours. Thus the presence of hepatic tissue in testicular germ cell tumours has not been reported. In a series of 37 non-seminomatous testicular tumours seven tumours contained epithelial structures showing morphological and functional resemblance to liver cell trabeculae. These structures were present in tumours with yolk sac tumour (YST) components and most of the tumours also contained teratoid elements. With the immunoperoxidase technique the epithelial structures were heavily stained for alpha-foetoprotein (AFP) and ferritin in all cases, while positive staining for albumin, prealbumin and transferrin was occasionally found. Alpha-I-antitrypsin and haemoglobin F were demonstrated in few scattered cells. Whether or not these epithelial structures should be included among the various patterns of YST or considered to be teratoid components is uncertain. It is suggested that examinations of the heterogeneity of the concomitant serologic AFP may support one or other assumption.