Occult malignancy in neonatal sacrococcygeal teratomas. A report from a Combined Pediatric Oncology Group and Children's Cancer Group study.

Purpose: Six children who had mature or immature sacrococcygeal teratomas diagnosed in the newborn period have since been registered on a Pediatric Oncology Group/Children's Cancer Group germ cell study with recurrent malignant neoplasia [pure yolk sac tumor (YST) or teratoma with yolk sac elements].

Results: Four of the children have responded to therapy, one has died, and one has been lost to follow-up. Review of the slides from five of the original tumors identified microscopic foci of YST in four.

Conclusions: Detection of such foci in neonatal tumors is important because serum alpha-fetoprotein concentrations may not be helpful since they may normally be high in the newborn period due to fetal production.