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Cancers arising from keratinocytes or their precursors, which include basal cell carcinoma (BCC) and squamous cell skin carcinoma (SCC) of the skin, are the mostly frequently diagnosed malignancies in fair-skinned populations. These malignancies are commonly referred to as nonmelanoma skin cancers or simply skin cancers. This chapter reviews the epidemiology of keratinocyte carcinomas. Topics covered include demographic patterns, environmental factors, molecular genetic characteristics of tumors, and preventive measures.

Keratinocyte cancers (KC) include basal and squamous cell carcinomas that arise from keratinocytes or their precursors. KCs are the most common malignancies in humans. Basal cell carcinoma (BCC) has higher incidence rates, but squamous cell carcinoma (SCC) causes most deaths. Despite increasing incidence rates, the mortality rates have not changed markedly in recent years. The geographic and demographic features of these tumors have remained consistent over the past several decades, with a gradient of increasing incidence rates with proximity to the equator, predominantly affecting fair-skinned populations. Risk increases with age, is higher in men than women, and is associated with artificial as well as natural exposure to UV light. There is emerging evidence that these malignancies, particularly BCCs, may be increasing in younger adults and among women. While basal and squamous cell carcinomas share etiological factors, the relative importance of these factors, pattern of exposure, molecular alterations, and even the factors themselves differ.

This chapter discusses skin and soft tissue tumours. Three known skin tumours are the basal cell carcinoma, the squamous cell carcinoma, and the melanoma. Basal cell carcinoma or rodent ulcer predominantly affects the elderly and is rarely a clinical problem except in a few neglected cases and in cases where there is an extensive invasion of the local soft tissues and bones. Squamous carcinoma emerges in middle-aged and elderly patients. Compared to basal cell carcinoma, squamous carcinoma spreads in the local and regional nodes and may develop blood-borne metastases. Melanoma, the most potent of the three skin tumours affects any age, although it is rare in children. It is associated with excessive sun exposure. This disease has rapid blood-borne metastases and can cause rapid death.

Ultraviolet (UV) radiation is the principal cause of over 95% of keratinocyte cancers (basal cell carcinomas and squamous cell carcinomas of the skin), the most common cancers in white populations worldwide. UV radiation also causes an estimated 60%–90% of cutaneous melanoma, the cancer affecting the skin’s pigment-producing cells. In addition, UV radiation is the major cause of many eye diseases, including ocular cancers and cataract, the commonest cause of blindness, and is responsible for the underlying changes in skin aging, on which billions of dollars are spent annually in efforts to repair the damage. The sun is the principal source of human exposure to UV radiation. However, artificial sources are encountered in a wide range of industrial and medical settings, and increasingly from commercial tanning facilities. By the late twentieth century, nearly epidemic increases in skin cancer incidence had occurred in white populations, especially in Australia and New Zealand.

Questions

52-year-old man presents to the clinic for review some six weeks after starting phenytoin for complex partial seizures. He is very concerned as he has a rash which began on his face but quickly spread over the upper body. It begins as large,...

Basic sciences: Applied anatomy

Which among the following statements concerning the lymphatic drainage of the colon is incorrect?

Lymph from the intermediate mesocolic lymph nodes drain to the principal nodes

Lymph from the caecum drains into the principal nodes at the origin...