Teratomas: Embryonal Carcinomas/ Teratocarcinomas

Teratomas of the testis (Fig. 1.139) are frequent in 129/ Sv-ter+ mice (currently named 129S4/SvJae, and other lines derived from Stevens), with up to 10% of mice affected by 3 weeks of age. Up to 94% of older ter+/+ homozygous mice may have testicular teratomas, with up to 75% with bilateral involvement. Extragonadal teratomas arise in the perigenital region or midline of chimeras derived from 129 embryonic stem cells. Ter­atomas characteristically contain tissue elements derived from ectoderm, mesoderm, and endoderm (Fig. 1.140).