Mature Teratoma Confined to the Posterior Fossa.

Mature teratomas located solely in the posterior fossa are rare. We describe a girl who presented with hydrocephalus caused by a posterior fossa tumor that was ultimately diagnosed as a mature teratoma following complete extirpation. Unusual imaging characteristics which produced confusion preoperatively were, however, very consistent with mature teratomas that are encountered in the gonads. Immature elements were universally absent; therefore, extirpation was curative. Hydrocephalus is unlikely to resolve after tumor removal, and cerebrospinal fluid diversion may be required.