Neuroblastoma is a cancer of the sympathetic nervous system, a nerve network throughout the body which carries messages from the brain. Neuroblastoma is a solid, malignant tumor which manifests as a lump or mass in the abdomen or around the spinal cord in the chest, neck, or pelvis. Neuroblastoma is often present at birth, but is most often diagnosed much later when the child begins to show symptoms of the disease. A condition known as "opsoclonus-myoclonus syndrome" can sometimes be a symptom of neuroblastoma. It is bursts of rapid and involuntary, chaotic eye movement in all directions. It's important to note that not all children with this syndrome have neuroblastoma. In the majority of cases (73%), neuroblastoma has already spread to area's outside of the original site at the time of diagnosis.