Update on Keratinocyte Carcinomas

Basal-cell carcinoma and cutaneous squamous-cell carcinoma are the most common skin cancers worldwide. Although the term nonmelanoma skin cancer has traditionally been used to refer to all skin cancers except melanoma, “keratinocyte carcinoma” is becoming the preferred term for basal-cell carcinoma and cutaneous squamous-cell carcinoma because of the shared lineage with epidermal keratinocytes.1 Moreover, “keratinocyte carcinoma” is a more specific term than “nonmelanoma skin cancer” and more accurately differentiates basal-cell and cutaneous squamous-cell carcinomas from other skin cancers such as Merkel cell carcinoma, adnexal carcinoma, and derma-tofibrosarcoma protuberans. Despite similarities between basal-cell carcinoma and cutaneous squamous-cell carcinoma, it is important to note that high-risk cutaneous squamous-cell carcinoma is biologically distinct and requires different clinical management. In the United States, the total number of basal-cell carcinomas and cutaneous squamous-cell carcinomas diagnosed annually far exceeds the number of all other cancers combined.2 Population studies have shown an increasing incidence, with the highest rates in Australia (>1000 basal-cell carcinomas per 100,000 person-years) as compared with parts of Africa (<1 basal-cell carcinoma per 100,000 person-years).3 The individual risk of keratinocyte carcinoma varies with the amount of exposure to ultraviolet (UV) radiation, age, skin pigmentation, and recreational behavior. Whereas death from basal-cell carcinoma is uncommon, death from cutaneous squamous-cell carcinoma is becoming a major component of cancer-related mortality among the elderly and immunosuppressed patients. Moreover, disfigurement from primary tumors, particularly on the head and neck, may have a profound effect on quality of life. Keratinocyte carcinomas represent an important public health challenge and economic burden, requiring careful evaluation of treatment and prevention strategies. Copyright © 2018 Massachusetts Medical Society.