The first symptoms of neuroblastoma are often vague and may include fatigue and loss of appetite. As the disease progresses, symptoms will depend on the location of the tumor. A tumor in the abdomen may cause a swollen belly, stomach pain, constipation, or diarrhea. A tumor in the chest may cause breathing problems. Tumors pressing on the spinal cord may cause weakness or difficulty walking. Some children experience bone pain, and some may have unexplained "black eyes" or bulging eyes. Many of these symptoms are similar to those of other more common illnesses. Half of all neuroblastomas have already spread to other parts of the body by the time a diagnosis is made.