The author studied 153 cases of intracranial germ cell tumors (GCTs) through 1994, 62.7% of which showed monotypic histological patterns and 37.3% of which were shown to be mixed tumors. All of these cases, except for six patients who died soon after admission and underwent autopsy, underwent surgery followed by radio- and/or chemotherapy. All patients with choriocarcinoma died within 2 years. Patients with yolk sac tumor (endodermal sinus tumor) and embryonal carcinoma also had poor outcomes. Patients with mature teratoma had 5- and 10-year survival rates of 92.9% each. Patients with immature teratoma and malignant teratoma had a 5- and 10-year survival rate of 70.7% each. Patients with germinoma had a 5-year survival rate of 95.4% and a 10-year survival rate of 92.7%. These results may bring into question the validity of the germ cell theory, because germinoma, which should be the most undifferentiated according to the theory, was the most benign and choriocarcinoma and yolk sac tumor (endodermal sinus tumor), which should be the most differentiated, were the most malignant according to results obtained during follow-up study.
Therefore, GCTs other than germinoma may not originate from one single type of cell (primordial germ cells). The embryonic cells of various stages of embryogenesis may perhaps be misplaced in the bilaminar embryonic disc at the time of the primitive streak formation, becoming involved in the stream of lateral mesoderm and carried to the future cranial area to become incorrectly enfolded into the brain at the time of the neural tube formation. The authors propound the following law: tumors composed of cells resembling the cells that appear in the earlier stages of embryogenesis (ontogenesis) are more malignant than those composed of cells resembling the cells that appear in the later stages of embryogenesis.
The incidence of yolk sac tumor (endodermal sinus tumor) elements in germ cell tumors of the testis in adults
