Neoplasia of early life and its relationships to teratogenesis.

: The biologic peculiarities of tumors of early life are elucidated. The oncogenic grace period is emphasized, wherein infantile tumors tend to behave in a relatively benign fashion up until 3-6 months of age. A review of the types of congenital malformations associated with the development of neoplasms is presented. These associations appear to be of fundamental importance in developmental pathobiology. They are illustrated by the tendency for neoplasms to develop in anomalous or dysplastic tissues, such as developmental vestiges, undescended testes, dysgenic gonads and certain hamartoses. There is an increased incidence of tumor occurrence in: (1) specific teratologic disorders: aniridia, hemihypertrophy, Beckwith's syndrome, basal cell nevus syndromes and others; (2) cytogenetic abnormalities: Down's syndrome, 13q- syndrome (D-deletion), trisomy 18; (3) chromosomal instability syndromes: Fanconi's anemia, ataxia-telangiectasia, Bloom's syndrome. Finally, many agents, known to be carcinogenic when administered postnatally to animals, are teratogenic in the fetus. A few agents--urethan, alkylnitrosoureas, estrogens--are both teratogenic and carcinogenic when administered to the fetus transplacentally. It is suggested that the timing of intrauterine insult is important in determining whether the effect on the offspring is teratogenic, oncogenic or both. Teratogenesis appears to be the more primitive response. Other theories explaining the concurrence of tumors and anomalies are offered.