Xeroderma pigmentosum (age 20)

Xeroderma pigmentosum (age 20)

Risk of Basal Cell and Squamous Cell Carcinoma

Standard Model of Carcinogenesis

The standard model of carcinogenesis invokes a tumor induction event, followed by a series of tumor promotion events.

• tumor induction
  • ultraviolet light as an inducer can be the ultraviolet light acquired in childhood

• tumor promotion
  • multiple promotion events are usually necessary following induction
  • additional UV light can be a tumor promoter
  • each additional promotion event leads to increased risk of cancer developing
  • promotion events are particularly important when they damage a cell rather than kill it

• basal cell carcinoma and malignant melanoma
  • very low doses of UVB increase cancer risk for basal cell carcinoma and malignant melanoma
  • childhood exposure can be very important to later life risk

• squamous carcinoma
  • is linked to the accumulation of a very large amount of ultraviolet light
  • risk is low with low amounts of exposure, and very high with large amounts of exposure
  • outdoor workers, and those active in sports, are at particularly high risk for squamous carcinoma