Molecularly targeted therapy for osteosarcoma: Where do we go from here?

Osteosarcoma at the molecular level is among the most complex pediatric -malignancies. Despite its relatively high incidence in the pediatric patient population many aspects of this disease continue to defy understanding. Osteosarcoma is the most common primary malignant bone tumor in children and adolescents (Arndt and Crist 1999). Approximately 400 children and adolescents are diagnosed each year in the United States (Meyers and Gorlick 1997). In the adolescent age range, it is the second most common malignancy, following only lymphoma in incidence. Osteosarcoma continues to be diagnosed solely based upon its histologic appearance. Despite having tremendously variable appearance, characterized descriptively by its histologic subtype, the presence of a malignant spindle cell which produces osteoid is the basis for diagnosing osteosarcoma. Molecular analyses of gene copy number, translocations, and gene expression do not contribute to making the diagnosis.