So-called intracranial germ cell tumours: personal experiences and a theory of their pathogenesis

Abstract

We investigated 110 cases of intracranial germ cell tumours (up to the end of 1986), 56% of which showed monotypic histological patterns and 44% were shown to be mixed tumours. All these cases underwent surgery followed by radiation and/or chemotherapy. All cases of choriocarcinoma and embryonal carcinoma died within 2 yr: cases of endodermal sinus tumour also showed poor results (4 yr survival rate was 12.5%). Mature teratoma had a 5 yr survival rate (5YSR) and a 10 yr survival rate (10YSR) of 78.3% each: immature teratoma showed a 5YSR of 44.9%. Two-cell pattern tumours (PTC) showed a 5YSR of 85.8% and a 10YSR of 82.4%. They (PTC) can be divided into two groups (i) germinoma and (ii) pinealoma of pineal parenchyma origin (pineocytoma with lymphocytic infiltration) on the basis of the difference in the tumour cell-stroma relationship and also placental alkaline phosphatase stain. In the pineal region, 70% of PTC belonged to the category of pinealoma and in the suprasellar region, 92% of PTC were germinoma. Germinoma showed a 5YSR of 91.4% and a 10YSR of 91.4%, whereas those of the pinealoma were 78.2% and 68.4% respectively. This suggests that the biological characteristics of germinoma and pinealoma may be different. 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 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 only one type of cell (primordial germ cells), except for the germinoma. The embryonic cells of various stages of embryogenesis may probably be misinvolved in the stream of lateral mesoderm at the time of the primitive streak formation and be carried to the future cranial area to be misenfolded into the cranium 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)’.