So-called intracranial germ cell tumours: are they really of germ cell origin?

We have studied 139 cases of intracranial germ cell tumours up to the beginning of 1993, 63.3% of which showed monotypic histological patterns and 36.7% were shown to be mixed tumours. All these cases underwent surgery followed by radiation and/or chemotherapy. All cases of choriocarcinoma died within 2 years. Cases of yolk sac tumour (endodermal sinus tumour) and embryonal carcinoma also showed poor results. Mature teratoma had a 5-year survival rate (5 YSR) and 10-year survival rate (10 YSR) of 92.9% each. Immature teratoma and malignant teratoma showed a 5-YSR and 10-YSR of 75.0% each. Germinoma showed a 5-YSR of 94.7% and a 10-YSR of 91.2%. All these results may bring into question the validity of the germ cell theory, since germinoma, which should be the most undifferentiated according to the theory, was the most benign and choriocarcinoma and yolk sac tumour (endodermal sinus tumour) which should be the most differentiated, were the most malignant in the follow-up study. Therefore, germ cell tumours may not originate from one single type of cells (primordial germs cells), except for germinoma. The embryonic cells of various stages of embryogenesis may perhaps be misplaced in the bilaminar embryonic disc and become involved in the stream of lateral mesoderm at the time of the primitive streak formation and be carried to the future cranial area to be wrongly enfolded into the brain at the time of the neural tube formation. The following law may be propounded: Tumours composed of cells resembling the cells appearing in the earlier stages of embryogenesis (ontogenesis) are more malignant than those resembling the cells appearing in the later stages of embryogenesis (ontogenesis).