At Mayo Clinic, your doctor will look at your lips, mouth, throat and nose for scales, sores, discoloration, hardening or numbness. You may need to have a small tissue sample removed (biopsy) for lab analysis to look for cancerous or precancerous cells. In some cases, a biopsy is part of surgical treatment rather than a separate procedure.
If your doctor suspects that cancer has spread beyond the surface of your lip, he or she may order one or more imaging tests, such as an X-ray, ultrasound, computerized tomography (CT) scan, magnetic resonance imaging (MRI) or a positron emission tomography (PET) scan. In tests that involve radiation, specialists carefully monitor doses to avoid the risk of radiation overexposure.