A person can get oral cancer without having any other type of cancer. However, oral cancer can also happen because of "metastasis". This means that the person had cancer in some other part of their body, and it spread to the mouth. The person's cancer may be far away from the mouth, or it may be in a part of the body that neighbors the mouth. For example, if a person has cancer of the nasal cavity, the cancer can spread to the mouth.