頭蓋内奇形腫の発生起源

ON THE ORIGIN OF INTRACRANIAL TERATOMAS

　抄録　頭蓋内奇形腫の発生起源を知る目的で自験例及び文献上報告されている新生児期の頭蓋内奇形腫（新生児型）とそれ以降の頭蓋内奇形腫（小児型）とを対象として，その年齢分布，発生部位，組織学的特徴を比較検討した。更に自験例で奇形腫とfetus-in-fetuの移行型と考えられる症例の特徴を自験例の典型的な新生児奇形腫及び此れ迄に発表された頭蓋内fetus-in-fetuとを対照に比較検討した。その結果以下の4点を得た。即ち，1）奇形腫の年齢別発生頻度のピークが新生児期と小児期（10歳代）の2つに見られる，2）奇形腫の発生部位が新生児型では松果体以外で前頭蓋窩〜前頭葉及び側脳室に多く，小児型では松果体〜第三脳室に圧倒的に多く，明らかな差が認められる，3）組織学的に，新生児型ではgerminomatouscomponentの混在が見られないのに対して小児型ではしばしば認められる，4） included twinであるfetus-in-fetuと奇形腫の移行型が存在する可能性がある。以上の結果から，頭蓋内奇形腫の中には発生起源を異にする2つの群が存在する可能性が強く示唆された。即ち，新生児型は先天奇形であるincluded twinに由来し，それ以降に発生する小児型はgerm cellに由来すると考えられる。

To investigate the origin of intracranial terato-mas, the author reviewed 245 reported cases of in-tracranial teratoma in neonates (onset of symptoms within 2 months after birth) including his own case and compared them with those occurring in child-hood registered in Brain Tumor Registry in Japan (onset of symptoms more than 2 months after birth) in terms of incidence, age distribution, locationsand histological pictures. An operated case of ter-atoma with digit formation and well organized tis-sue arrangement, a presumed transitional form bet-ween teratoma and fetus-in-fetu, is presented in de-tail and was compared with cases of typical neona-tal teratoma and a case of intracranial fetus-in-fetu documented in the literature as well. The follow-ing results were obtained : 1) There are two peaks in age distribution as to the incidence of intracra-nial teratomas, in the neonatal period and in child-hood (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 neo-natal teratomas though they are frequently obser-ved in childhood teratomas. 4) There are some cases showing transition between teratoma and fe-tus-in-fetu, which is believed to originate from in-cluded twins.

The results suggest that there are two pathoge-netically 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.