ABSTRACT
Their unique growth sites, characteristic subtypes with different histology, and high incidence in Japan render intracranial germ cell tumors fascinating. They grow at various brain sites as solitary masses or multiple foci; mostly occur in the pineal and neurohypophyseal (suprasellar) region; and they are rarely found in the basal ganglia or at other sites in the brain. Characteristically they include subtypes composed of cells that resemble those seen in the embryonic stage of development, i.e., trophoblast (in choriocarcinoma) that appear as early as the stage of blastocyte formation, yolk sac endoderm (in yolk sac-or endodermal sinus tumors), pluripotent stem cells (in embryonal carcinomas), differentiated embryonic cells (in teratomas), and primordial germ cells (in germinomas). Why choriocarcinoma, essentially a female cancer, grows in the brain of boys remains an interesting question. Epidemiologically, there is a difference in the incidence of these germ cell tumors; they represent 3.0% of all primary brain tumors in Japan (1) while the reported incidence in the United States is 0.6% (2). These features, not observed in other neuroectodermal or embryonal tumors of the brain, have attracted the attention of neuropathologists, neurosurgeons, and now tumor biologists.
