The diagnosis process for oral cancer begins with a physical examination. Whether or not symptoms are present, a dentist may notice an abnormal tissue change in the mouth during a routine check-up, feeling any lumps or masses.

Direct examination of the lesion or a small biopsy may establish a diagnosis. Once a diagnosis is made, the doctor will determine whether the cancer has spread beyond the oral cavity and the size of the cancer using various tests. These tests may include:

* MRI scan of the head and neck
* CT scan of the chest to look for cancer in the lymph nodes
* PET (Positron Emission Tomography) scan to look for cancer in other areas of the body
* The doctor may also examine the larynx, esophagus, and lungs by passing a tube with a small camera on the end down the throat.