chapter  44
Germ cell tumors
ByMarc K. Rosenblum
Pages 28

Listed in Box 44.1 as designated in the current World Health Organization (WHO) taxonomy (Rosenblum et al., 2000), germ cell tumors of the central neuraxis are now recognized in all their variety as the morphologic homologs of germinal neoplasms arising in the gonads, mediastinum and other extragenital sites. Ironically, inclusion in this group came belated to its most commonly occurring representative. We refer to the neoplasm known, after Friedman (1947), as germinoma. The only CNS germ cell tumor accorded an appellation differing from that extended to its gonadal counterparts – the testicular seminoma and ovarian dysgerminoma – this was originally dubbed a form of ‘pinealoma’ by Krabbe (1923), who held that the lesion was of specialized pineal parenchymal derivation. This misconception seems to have been based largely upon the fancied resemblance of a mosaic cellular architecture characterizing the fetal and neonatal pineal gland to the admixture of large and small cell forms typifying germinomas (Globus and Silbert, 1931). The latter, of course, are today appreciated as distinct populations of neoplastic germinal elements and reactive lymphocytes, respectively. The histologic similarity of this ‘two-cell type pinealoma’ to the testicular seminoma was first pointed out in the pathologic description of an example reported by Harris and Cairns (1932), with Dorothy Russell (1944, 1954) going on to explicitly link this entity and its suprasellar variant (‘ectopic pinealoma’) to

the emerging germ cell tumor series as an atypical form of teratoma. Accounts of the less prevalent species of CNS germ cell neoplasia, again, predated these important developments by many years. A century, in fact, separates us from the recognition of that rarest member of this company, the intracranial choriocarcinoma (Askanazy, 1906).