Lip: Upper and lower lip form the upper and lower anterior wall of the oral cavity. They consist of an exposed surface of modified epidermis beginning at the junction of the vermilion border with the skin and including only the vermilion surface or that portion of the lip that comes into contact with the opposing lip.
The lips extend from commissure to commissure and, for SEER Summary Stage include the mucous membrane lining the inner surface of the lips (labial mucosa). For staging, the labial mucosa is included with buccal cavity in the oral cavity staging scheme.
The most common type of malignant tumor of the lip is squamous cell carcinoma.