Skeletal metastasis: the effect on the immature skeleton.

The unique opportunity to study the entire appendicular skeleton of a child who died from metastatic angiosarcoma allowed detailed assessment of radiographically evident involvement. Virtually every portion of the appendicular skeleton had evidence of metastatic disease. However, the extent of involvement was extremely variable, especially when contralateral regions were assessed. The most likely region of metastasis, the metaphysis, is normally a fenestrated cortex of woven bone in the young child, rather than a well demarcated cortex formed by osteon (lamellar) bone, as it is in the adult. The pattern of destruction is such that less extensive areas may be involved before becoming radiographically evident, and trabecular bone involvement may be evident even without cortical damage. The metaphyseal metastatic spread supports the concept of arterial hematogenous dissemination, comparable to osteomyelitis in the child. Pathologic metaphyseal fractures involved both proximal humeri; the fracture also extended along a portion of the metaphyseal-physeal interface in one humerus. In one distal femur the physis readily separated from the metaphysis; this was a non-displaced type 1 growth mechanism injury.