A great number of paediatric tumours are biologically different from adult tumours. They are morphologically very similar to embryonic tumours, quickly invade surrounding tissues and form distant metastases. Moreover, they often are very sensitive to various chemotherapeutic regimens.
More often than not, there are no cancerogenic environmental factors and frequently these tumours are found with various deformities. Numerous genetic mutations are observed.
Originating from the embryonic neural crest, these tumours can be found in the retro-peritoneum and very rapidly produce distant metastases (in 60 to 70% of cases). The presence of secretion granules in their cytoplasm, visible using electronic microscopy, is very characteristic.
This is a relatively frequent kidney tumour, with a great variety of histologies which reproduce the various tissues which are present during embryogenesis.
1% of cases are found in a familial context, with bilateral lesions which might be due to the autosomic dominating transmission of an unknown gene.
Rhabdomyosarcomas are relatively frequent soft tissue sarcomas which differentiate towards the skeletal muscle. They form massive tumours (in the neck, the retro-peritoneum, the pelvis) and give rise to early distant metastases.
There are no familial forms, however a chromosome change is often observed with a translocation of chromosome 2 towards chromosome 13. In 1959, Li and Fraumeini described the frequent association of rhabodmyosarcoma arising in children with mothers having suffered from breast carcinoma.
Retinoblastoma is a rare childhood tumour originating from the embryonic retina epithelium. The hereditary history of certain forms have led Knudson to propose his theory of tumour suppressor genes.
10% of cases are in a family context and 10% of patients without a familial context bear a germinal abnormality which they transmit to their children. If patients are cured of their retinoblastoma, 20 to 30 years later, they may develop other tumours such as osteosarcomas.
In the familial form, one of the parents transmits an Rb inactive gene. A second mutation of the active allele (from the other parent) will lead to complete inactivation of the pRb protein. Non familial forms are due to a mutation of both alleles of Rb gene. Thus, generally, only the familial forms may present as a bilateral retina lesion.
Because Rb transmission can be thoroughly studied, precise genetic counselling can be provided for patients and their families..