Randal S. Weber, MD, is Hubert L. and Olive Stringer Distinguished Professor of Cancer Research and Chairman of the Department of Head and Neck Surgery at the University of Texas M. D. Anderson Cancer Center in Houston.
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July 2007Non-melanoma skin cancer is the most common malignancy afflicting humans, and is a major public health problem in the United States. The majority occur in the head and neck region due to the significant amount of actinic exposure received through recreational and work-related activities. Fortunately, the less aggressive basal cell carcinoma of the skin occurs at four times the incidence of cutaneous squamous carcinoma. Males predominate for both histologic types, likely because of the increased sun exposure they receive. Although mortality for non-melanoma skin cancer is low, morbidity is significant because of the cosmetic and functional sequelae that may occur following surgical resection and reconstruction in the treatment of aggressive lesions. It is estimated that 2000 deaths annually are attributable to non-melanoma skin cancer, but this figure is only an estimate, as incidence and mortality of non-melanoma skin cancer are no longer tracked in the national cancer databases.
Compared to squamous cell carcinoma of the skin, basal cell carcinomas tend to remain localized and rarely metastasize to regional lymph nodes. Tumor spread along regional nerves (perineural invasion) in the head and neck occurs in both squamous and basal cell carcinoma in approximately 15% and 0.1% of cases, respectively, but is associated with a high rate of local recurrence and regional and distant spread. Most basal cell carcinomas tend to remain localized; however, the infiltrative type previously referred to as morphea is more aggressive and has a higher recurrence rate. In contrast, squamous carcinoma of the skin is more biologically aggressive and has a propensity to spread along nerves and metastasize to regional lymph nodes in approximately 15% of patients. Clayman et al.1 demonstrated in a prospective clinical pathologic study that patients with squamous carcinomas of the skin that are greater than 4 cm in diameter, invade into the underlying subcutaneous tissue and bone, or exhibit perineural invasion are associated with a 40% two-year mortality rate. Non-melanoma skin cancers with any of these features are defined as aggressive non-melanoma skin cancer.