© 2005-2012 American Society of Clinical Oncology (ASCO). All rights reserved worldwide.
A risk factor is anything that increases a person's chance of developing a tumor. Although risk factors often influence the development of a tumor, most do not directly cause a tumor. Some people with several risk factors never develop a tumor, while others with no known risk factors do.
Doctors don't know what causes most childhood cancers, including medulloblastoma. Medulloblastoma is more common in boys than in girls. It occurs most often in the first eight years of life, with about half occurring in children younger than six years old.
In rare situations, children with nevoid basal cell carcinoma syndrome (NBCCS), a hereditary condition also known as Gorlin syndrome, have an increased risk of developing medulloblastoma. People with NBCCS are more likely to develop various tumors.