Histogenetic considerations concerning germ cell tumours. Morphological and immunohistochemical comparative investigation of the human embryo and testicular germ cell tumours.

Although it is accepted that the different components of germ cell tumours (GCT) imitate the embryonic and extraembryonic structures in early development, various tumour patterns remain to be interpreted in histogenetic terms. In particular, some patterns of embryonal carcinoma (EC) and yolk sac tumour (YST) have not been given a convincing histogenetic explanation. Combined morphological and immunohistochemical studies of GCT in addition to a three-dimensional analysis permit correlations between certain tumour patterns and normal embryonic and extraembryonic structures to be made. The various tumour patterns which reflect various stages of differentiation or maturation of cells and tissues of the normal conceptus may also be placed in chronological order with regard to embryogenesis. On the basis of such considerations a nomenclature using the embryological terms for the various tumour components may be considered, although not recommended as a new system of classification.