A chordoma tumor is a type of cancer that develops in the skull or spine, according to the Mayo Clinic. Chordomas are very rare bone tumors and affect only eight out of every 10 million people in the United States, states WebMD.
Chordomas are a type of cancer known as sarcomas that develop from connective tissues such as bone, cartilage or muscles. There are no environmental or behavioral risk factors associated with chordoma, says The Chordoma Foundation. Rather, genetic risk factors may influence a person's likelihood of developing the disease. The median overall survival for people diagnosed with chordoma is seven years.