Abdominal, retroperitoneal and sacrococcygeal tumours of the newborn and the very young infant. Report from the Kiel Paediatric Tumour Registry.

We examined 226 abdominal, retroperitoneal and sacrococcygeal tumours in newborns and infants aged 6 months or less. Most frequent were neuroblastomas (n = 83) followed by germ cell tumours (n = 76), 37 of which were immature and 32 were mature teratomas. Fully malignant germ cell tumours and malignant germ cell tumour components were much rarer in this age group (9.2%) than in older children (58.1%). The majority of germ cell tumours were localized in the sacrococcygeal region (72.4%). Next in frequency were tumours of the kidney (n = 54), including 28 congenital mesoblastic nephromas. In contrast to children over 6 months of age, kidney tumours were frequently low grade malignant with a favourable prognosis. Among liver tumours there were 19 infantile haemangioendotheliomas and 9 hepatoblastomas. By contrast, at ages 7-24 months hepatoblastomas (n = 28) were much more frequent than haemangioendotheliomas (n = 2). Tumours in the newborn and very young infant differ from those in older children in many respects: (1) the relative frequency; (2) localization; (3) distribution of histological types; (4) degree of differentiation, often associated with a tendency toward maturation but occasionally also with increasing malignancy; and (5) prognosis, which is comparatively favourable.