Bone metastasizing renal tumor of childhood: morphological and clinical features, and differences from Wilms' tumor.

A bone metastasizing primary renal tumor of childhood is described, and five cases are presented. Although all five cases were originally diagnosed as nephroblastomata, there appear to be sufficient histological, ultrastructural and clinical differences to suggest that these tumors should comprise a separate and distinct entity. Using the data from the Manchester Children's Tumor Registry, the incidence of this tumor was found to be 2.3% of all primary renal neoplasms in childhood.