Squamous cell carcinoma (Fig. 13.36)
Predisposing factors include smoking or chewing tobacco products, and the ‘straight-shot’ drinking of alcohol. Cancer can also occur in the plaques and ulcers of lichen planus. Lip cancers may be sun-induced.
A thickening or nodule develops, usually on the lower lip, and often in a field of actinic chelitis (rough scaling mucosa from sun damage). Inside the mouth, the tongue is the most common site to be affected, often on its undersurface. The cancer itself appears either as an indurated ulcer with steep edges, or as a diffuse hardness or nodule. Red or white thickened plaques are common precursors, and the cancer may be surrounded by these changes.
Unfortunately, cancer of the mouth often goes undetected. Its symptoms are excused by the patient as aphthous ulcers or denture sores, and its signs are not seen by the physicians who scan the skin. Cancers grow, and squamous cell carcinomas of the mouth are no exception. Plaques and hard areas may ulcerate.
Confusion occurs with ulcerative lichen planus and other causes of white and red patches. Biopsy will dif-ferentiate a squamous cell carcinoma from these other conditions.
Dermatologists often treat lip cancers by a wedge excision through all layers of the lip, with primary repair. Oral surgeons or otolaryngologists usually remove intraoral cancers. Metastatic disease may require radiotherapy or chemotherapy.
Squamous cell carcinomas of the lip caused by sun exposure carry a much better prognosis than the others. Left untreated, squamous cell carcinomas are prone to metastasize to regional lymph nodes and elsewhere. The overall 5-year survival for intraoral squamous cell carcinoma is about 40 –50%.