Actinic Keratosis (AK): Microscopical and Genetic Features

abbreviation: AK=Actinic Keratosis; SCC=Squamous Cell Carcinoma

Why the environment is so unhealthy in AK ?
-Keratinocytes exposed to UV light lead to the generation of CPDs (Cyclobutane Pyrymidine Dimers) 6,4 photoproducts
-In AKs Langerhans cells (dendritic cells, histiocytes) are less present which gives lowers the immunity which allows proliferation to go unchecked and a progressive accumulation of mutations

Genetic features of AK
-Ak and SCC have p53 and p16 (gene suppression) mutations.
-Normally functional p53 and p21 induce cell cycle arrest to allow DNA repair or apoptosis if damage is too important
-Thus deficient repair mechanisms enables DNA to replicate and genetic damage to accumulate (Single cell mutations induce clonal expansion)

Microscopically (Histopathology of AK)
-AK looks like skin cancers in situ, that is also like Bowen’s disease (SCC in situ)
–Solar Elastosis
-82-97% of SCCs are contiguous with AKs when there is a history of solar damage

Routine eradication is unnecessary Cockerell (USA). CN09: Actinic Keratoses – I sroutine eradication Necessary ?World Congress of Dermatology 2015 –  Vancouver, Canada