ACTINIC keratoses are proliferations of transformed, neoplastic keratinocytes that are confined to the epidermis and induced by exposure to UV radiation in sunlight. Neoplastic transformation occurs in keratinocytes that have been exposed to UV radiation and is due primarily to mutations in the p53 gene. In time, these cells proliferate in the epidermis and eventually extend into the dermis, at which point metastatic spread can occur. Cytologic atypia is visible in early stages and is identical to that seen in metastatic lesions or in squamous cell carcinoma in the dermis. While these cells remain confined to the epidermis, the lesions that they cause are termed actinic keratoses, but when they extend more deeply to involve the papillary and/or reticular dermis, they are termed squamous cell carcinoma. The term actinic keratosis was developed on the basis of the clinical appearance and texture of these lesions, without regard to histopathologic or pathologic findings. Actinic keratoses are malignant neoplasms in evolution that demonstrate histologic and molecular genetic changes of such. Consideration should be given to adopting a new term, such as keratinocytic intraepidermal neoplasia or solar keratotic intraepidermal squamous cell carcinoma, to better define these lesions.
Fu W, Cockerell CJ. The Actinic (Solar) KeratosisA 21st-Century Perspective. Arch Dermatol. 2003;139(1):66-70. doi:10.1001/archderm.139.1.66