Due to its prominent location on the face, cancer of the lip is usually diagnosed early and is usually successfully treated. The American Joint Committee on Cancer defines the lips as part of the oral cavity that “begins at the junction of the vermilion border with the skin and includes only the vermilion surface or that portion of the lip that comes into contact with the opposing lip.” Unlike other malignancies of the oral cavity, cancer of the lip is more likely due to the cumulative damage caused by ultraviolet (UV) radiation than by tobacco and alcohol abuse. The lips are especially vulnerable to UV radiation as they lack a protective pigmented layer. Prolonged exposure to sunlight has been shown to cause a loss of elastic fibers, atrophy of the vermilion, as well as hyperkeratosis and atypia of the underlying cells. Severe UV damage can result in actinic cheilitis of the lips (chronic scaling and crusting of the vermilion) similar to actinic keratoses seen in sun-damaged skin.

There is a higher incidence of cancer of the lower lip (>85%) than the upper lip (2% to 7%) and oral commissure (<1%) presumably due to the greater UV exposure of the lower lip. Carcinoma of the lip typically presents as
a nonhealing erythematous lesion on the lower lip. The lesion may have perioral chapping or crusting and may ulcerate and bleed in advanced stages. Cancer of the lip tends to remain localized for extended periods of time, and most (80% to 90%) present as stage T1 or T2 with growth occurring laterally rather than invading deeply. Bimanual palpation of the lip can give an accurate assessment of its size, especially if the lesion is ulcerated. Inspection of the gingiva and palpation of the teeth should be performed to insure that the tumor has not extended beyond the confines of the lip. A thorough palpation of the nodal basins of the neck is indicated in all but the most superficial lip cancers. The medial portions of the lower lip drain primarily into the submental lymph nodes, while the lateral portions drain primarily into the lymph nodes of the submandibular triangle (Levels Ia and Ib). There are numerous anastomoses between the lymphatic channels of the lower lip, which allows for bilateral metastases from tumors that are on or near the midline. In contrast, there is sparse crossing of the lymphatics of the upper lip. The upper lip drains primarily into the ipsilateral nodal basins of the periparotid, submental, and submandibular lymph nodes. These nodes in turn drain into the upper and middle deep jugular nodes (Level II/III). A thorough examination of the head and neck is routinely performed to look for any second primary cancers.

Perineural invasion of the trigeminal nerve is a relative contraindication for surgical resection if there is extensive involvement of the nerve on preoperative imaging. Ionizing radiation along the entire length of the nerve up to and including the skull base is indicated in these patients, and the primary cancer can be included in the radiation field. In those patients in whom functional and cosmetic results would be compromised by surgical resection, radiation therapy can be used as a primary treatment modality. Lesions that involve more than one-third to one-half of the lip require additional local flap reconstruction and should be considered for more extensive surgery (Fig. 1.2).