[On the origin of intracranial teratomas].

To investigate the origin of intracranial teratomas, the author reviewed 245 reported cases of intracranial teratoma in neonates (onset of symptoms within 2 months after birth) including his own case and compared them with those occurring in childhood registered in Brain Tumor Registry in Japan (onset of symptoms more than 2 months after birth) in terms of incidence, age distribution, locations and histological pictures. An operated case of teratoma with digit formation and well organized tissue arrangement, a presumed transitional form between teratoma and fetus-in-fetu , is presented in detail and was compared with cases of typical neonatal teratoma and a case of intracranial fetus-in-fetu documented in the literature as well. The following results were obtained: 1) There are two peaks in age distribution as to the incidence of intracranial teratomas, in the neonatal period and in childhood (10 years of age), respectively. 2) Teratomas in neonates mostly arise in the frontal lobe and/or frontal base and the lateral ventricle comprising about 29% of all cases whereas those occurring in childhood arise mostly in the pineal region (56%). 3) No germinomatous components are seen in neonatal teratomas though they are frequently observed in childhood teratomas. 4) There are some cases showing transition between teratoma and fetus-in-fetu , which is believed to originate from included twins. The results suggest that there are two pathogenetically different forms of intracranial teratomas: the one in the neonate originates from included twins and the other, which occurs in childhood originates from germ cells.