In spite of the 50% lower ALA content BF-200 ALA triggers significantly higher PpIX concentrations than the 20% ALA formulation, indicating that clinical efficacy with BF-200 ALA may be higher. Moreover, the ex vivo eyelid skin model may represent a useful tool to investigate drug permeation in human skin.

Background Mutations in kinetochore gene KNSTRN accelerate the development of cutaneous squamous cell carcinoma (SCC) and may correlate with different histological classifications of actinic keratosis (AKs). Objective To determine KNSTRN gene mutation frequency in healthy skin (HS), actinically damaged skin (ADS), in AKs with different histomorphological gradings and invasive SCCs. Methods All samples were histologically evaluated. AK lesions were additionally classified according to their upwards (AK I–III) and downwards (PRO I–III) directed growth pattern. Mutation analyses of all samples were performed using the Sanger method. Results With one exception, all detected mutations in KNSTRN gene showed an alanine‐to‐glutamate substitution at codon 40 (p.Ala40Glu). p.Ala40Glu mutation was found in 6.9% (2/29) of HS, in 16.1% (5/31) of ADS, in 18.3% (20/109) of AKs and in 30.0% (9/30) of invasive SCCs. Further stratification of AKs using the common AK classification of Röwert‐Huber revealed the p.Ala40Glu mutation in 14.7% (5/43), 13.3% (4/30) and 24.4% (11/45) (AK I, II and III). In contrast, the new PRO classification showed a distribution of 3.6% (1/28) in PRO I, 21.7% (13/60) in PRO II and 28.6% (6/21) in PRO III. Mutation frequency in HS showed significant differences compared to AKs classified as PRO III and invasive SCCs (P < 0.05). In contrast, there were no statistically significant differences between HS and AKs when classified according to Röwert‐Huber. Conclusions Recurrent somatic mutation p.Ala40Glu in KNSTRN gene is associated with basal proliferating AKs in accordance with invasive SCCs. This supports the impact of basal proliferative pattern in terms of progression.

Not Available Study supported by Biofrontera.