TeratomaReproducibility of ResultsObserver VariationTesticular NeoplasmsSacrococcygeal RegionMonitoring, PhysiologicDermoid CystMediastinal NeoplasmsElectric ImpedanceNeoplasms, Germ Cell and EmbryonalDysgerminomaAbsorptiometry, PhotonOvarian NeoplasmsRetroperitoneal NeoplasmsSensitivity and SpecificityEmbryonic Stem CellsBody CompositionGerminomaAbnormalities, Severe TeratoidReference ValuesQuestionnairesPredictive Value of TestsSeverity of Illness IndexIsochromosomesMesonephromaStruma OvariiProspective StudiesCoccyxPluripotent Stem CellsOvarian CystsInduced Pluripotent Stem CellsRetroperitoneal SpaceCell Differentiationalpha-FetoproteinsEndodermal Sinus TumorNeoplasms, Multiple PrimaryOctamer Transcription Factor-3SOXB1 Transcription FactorsChoriocarcinomaParaneoplastic Syndromes, Nervous SystemSpinal NeoplasmsTomography, X-Ray ComputedTwins, ConjoinedSeminomaCarcinoma, Embryonal