Glossary

Actinic keratoses: The early beginnings of skin cancer that have potential to progress to invasive squamous cell carcinoma. This most common lesion of the outermost layer of the skin is caused by long-term exposure to sunlight (specifically to ultraviolet wavelengths). Fair-skinned persons are at highest risk.

Cutaneous horn: An extreme, highly visible form of actinic Keratoses.

Keratinocytes: The tough-walled skin cells that make up more than 90 percent of the outer layer of the skin (epidermis).

Squamous cell carcinoma: The second most common skin cancer of the epidermis. Long-term exposure to solar radiation is regarded as a causative factor in squamous cell carcinoma. Actinic keratoses are lesions that are the early beginnings of skin cancer and may progress to invasive squamous cell carcinoma.

Ultraviolet radiation: The "sunburn" and "suntan" wavelengths of solar radiation. Ultraviolet radiation is the skin-damaging spectrum of sunlight.

An educational program brought to you by the American Academy of Dermatology.