Extraneural metastases in childhood brain tumors.

Although extraneural metastases are known to occur with primary tumors of the central nervous system, they are considered a rarity. Large autopsy series have placed the frequency at 0.4 to 0.5%. At the Roswell Park Memorial Institute, 36 children with brain tumors have been treated with a combination of surgery, radiotherapy, and chemotherapy in the past 12 years. We recently reviewed the autopsies obtained on 15 of these children and found that 4 (26%) had extraneural metastases. An additional child, who was not autopsied, had extraneural extension diagnosed during life. This inordinately high incidence of metastases outside the nervous system in children with aggressively treated brain tumors raises questions about their cause. The prolonged survival of these patients may have allowed growth of sufficient generations of extracranial metastatic cells for the extraneural disease to become clinically significant. Another possibility is that chemotherapy may alter the patients' immune system and thus promote extracranial tumor growth. As larger numbers of childhood brain tumors are managed with multimodality therapy, it may be possible to evaluate the extent to which treatment allows intracranial neoplasms to spread outside the nervous system.