Wilms' tumor and neuroblastoma are the two commonest abdominal neoplasms encountered in early life.10,11 Wilms' tumors arise from mesodermal cell rests within the kidney itself and therefore are tumors intrinsic to the kidney. Neurblastomas arise from neural crest tissue either in the adrenal medulla or from ganglion cells at any site along the sympathetic chain and therefore are extrinsic to the kidney. The differential diagnosis is based on the location of the soft tissue mass within or without the kidney.
Relative Frequency.—
The total number of neuroblastomas encountered in childhood exceeds the number of Wilms' tumors. However, the neuroblastoma, arising as it does from any sympathetic ganglion along the entire chain, may be found in the neck, thorax, abdomen, and pelvis. About 70% of all neuroblastomas arise from the adrenal medulla or upper-abdominal sympathetic ganglia. Therefore, when speaking only of upper-abdominal masses, the incidence of Wilms' tumor and that