Lack of genetic homozygosity in prepubertal teratomas: divergent pathogenesis distinct from that of teratomas in adolescents

In adults, both immature and mature ovarian teratomas show frequent genetic homozygosity consistent with tumorigenesis involving germ cells after meiosis I. Investigation into genetic zygosity of various teratomas in children has been limited. Thirteen sacrococcygeal, 12 ovarian, and 3 testicular teratomas in children 18 years or younger were retrieved from our departmental archives and histologically reviewed. Tumor and paired normal tissues were microdissected and subjected to short tandem repeat (STR) genotyping. DNA genotyping was informative in 12 sacrococcygeal teratomas, 8 ovarian teratomas, and 3 testicular teratomas. Sacrococcygeal teratomas included seven mature teratomas, four immature teratomas, and one mixed germ cell tumor with patient age ranging from 0 days to 3 years. All but two patients were female. Ovarian teratomas included five mature and three immature teratomas with patient age ranging from 2 to 18 years. Testicular teratomas included two mature teratomas and one immature teratoma with patient age ranging from 3 months to 3 years. All sacrococcygeal, testicular, and ovarian teratomas in patients younger than 4 years showed no evidence of genetic homozygosity by STR genotyping. In contrast, all four ovarian teratomas in patients older than 9 years showed either partial or complete homozygosity. In conclusion, unlike adolescent and adult ovarian teratomas, prepubertal sacrococcygeal and gonadal teratomas lack genetic homozygosity, supporting the hypothesis that teratomas before puberty develop at an early stage of germ cell development different from that of teratomas in adolescents and adults.